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12 pages, 9379 KiB

Open AccessArticle

Compression Properties of Interlayer and Intralayer Carbon/Glass Hybrid Composites

by Qingtao Wang, Weili Wu and Wei Li

Polymers 2018, 10(4), 343; https://doi.org/10.3390/polym10040343 - 21 Mar 2018

Cited by 11 | Viewed by 4072

Abstract

The compression properties and mechanisms of interlayer and intralayer Carbon/Glass (C/G) hybrid composites were investigated in this work. As revealed from the experimental results, the compression modulus increases linearly with the increase of carbon fiber content, following the rule of mixtures (ROM). The [...] Read more.

The compression properties and mechanisms of interlayer and intralayer Carbon/Glass (C/G) hybrid composites were investigated in this work. As revealed from the experimental results, the compression modulus increases linearly with the increase of carbon fiber content, following the rule of mixtures (ROM). The C/G hybrid ratio is regarded as the decisive factor for the compression modulus of hybrid composites. The positive mixing effect exists on compression strength for interlayer and intralayer hybrid composites, whereas the experimental values are above the theoretical calculation values. The compressive strength of interlayer hybrid composites taking on various hybrid structures differs largely at the same mixed ratio, at which the compressive strength of glass fiber sandwiching carbon fiber is higher than that of carbon fiber sandwiching glass fiber. Through comparing interlayer and intralayer hybrid composites, the impact exerted by layer structures on the compressive strength of interlayer hybrid composites is higher than that of intralayer hybrid composites, which leads to more designable characteristics for interlayer hybrid composites. This work makes it possible to optimize the compression strength of interlayer hybrid structures so that it achieves or basically exceeds pure carbon fiber composites. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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13 pages, 1335 KiB

Open AccessArticle

The Influence of Adhesive Compounds Biochemical Modification on the Mechanical Properties of Adhesive Joints

by Anna Rudawska, Izabela Haniecka, Magdalena Jaszek and Dawid Stefaniuk

Polymers 2018, 10(4), 344; https://doi.org/10.3390/polym10040344 - 21 Mar 2018

Cited by 16 | Viewed by 4854

Abstract

The main purpose of this paper was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of hot-dip galvanized steel sheet DX51+Z275 adhesive joints. The epoxy adhesives (resin and curing agent) were biochemically modified by lyophilized fungal [...] Read more.

The main purpose of this paper was to determine the effect of biochemical modification of epoxy adhesive compounds on the mechanical properties of hot-dip galvanized steel sheet DX51+Z275 adhesive joints. The epoxy adhesives (resin and curing agent) were biochemically modified by lyophilized fungal metabolites (in the form of lyophilized fungal fractions or materials preparation containing low molecular weight secondary metabolites of lignocellulose-degrading white rot fungi (WRF) Pycnoporus sanguineus (L.) Murrill and prepared by two methods). The epoxy adhesives (epoxy resin Epidian 53 and poliaminoamide curing agent PAC) were biochemical modified by lyophilized fungal metabolites and prepared by two methods. In the first method (Method I), the epoxy resin and the curing agent were mixed with the fungal material in the desired concentration. In the second method (Method II), the resin was mixed with mortar-grounded lyophilized post-culture liquid of the desired concentration and after following thorough mixing, a suitable amount of the poliaminoamide curing agent was added. The single-lap adhesive joints were prepared by modified epoxy adhesive compounds and were cured in various climatic factors. The specimens of adhesive joints were cured at single stage at the same temperature and humidity as during adhesive bonding (Variant A and Variant B). At the second stage, Method I adhesive joints were seasoned for two months at the temperature of 50 °C and 50% humidity in a climate test chamber (Variant C). The shear strength tests of the single-lap adhesive joints were performed using a Zwick/Roell Z150 testing machine in accordance with the DIN EN 1465 standard. The analysis of results revealed that the addition of the biological modifier can lead to reduced adhesive joint strength in ambient conditions, yet at elevated temperature and the higher humidity it results in a significant increase in adhesive joint strength. Full article

(This article belongs to the Collection Polymeric Adhesives)

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15 pages, 3663 KiB

Open AccessArticle

Long Range Polymer Chain Dynamics of Highly Flexible Polysiloxane in Solution Probed by Pyrene Excimer Fluorescence

by Janine L. Thoma, Jean Duhamel, Michael J. Bertocchi and Richard G. Weiss

Polymers 2018, 10(4), 345; https://doi.org/10.3390/polym10040345 - 21 Mar 2018

Cited by 10 | Viewed by 5745

Abstract

A poly(dimethylsiloxane-co-(3-aminopropyl)methylsiloxane) polymer (PDMS with 20.3 mol % of (3-aminopropyl)methyl siloxane monomer) has been labeled randomly with 1-pyreneacetyl groups to generate a series of polysiloxanes (Py-PDMS) with pyrenyl contents ranging from 0.7 mol % to 5.2 mol % of the total [...] Read more.

A poly(dimethylsiloxane-co-(3-aminopropyl)methylsiloxane) polymer (PDMS with 20.3 mol % of (3-aminopropyl)methyl siloxane monomer) has been labeled randomly with 1-pyreneacetyl groups to generate a series of polysiloxanes (Py-PDMS) with pyrenyl contents ranging from 0.7 mol % to 5.2 mol % of the total number of structural units. The remainder of the amino groups were acetylated to avoid intra-chain quenching of the excited singlet states of pyrene via exciplex formation with free amino groups while allowing the formation of excimers to proceed. The fluorescence spectra and temporal decays of the Py-PDMS samples were acquired in tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and dioxane. <k^MF>^blob, the average rate constant for intra-chain pyrene excimer formation, was determined from the analysis of the fluorescence decays. <k^MF>^blob was found to equal 1.16 (±0.13) × 10⁹, 1.14 (±0.12) × 10⁹, and 0.99 (±0.10) × 10⁹ s⁻¹ in THF, DMF, and dioxane, respectively, at room temperature. They are the largest values found to date for any polymeric backbone in these solvents. The qualitative relationship found here between <k^MF>^blob and the chemical structures of the polymers indicates that the luminescence characteristics of randomly labeled polymers is a very useful method to probe the long range dynamics of chains of almost any polymer that is amenable to substitution by a lumophore. Full article

(This article belongs to the Special Issue Polymer Characterization)

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13 pages, 3776 KiB

Open AccessArticle

Modification of Polyamide-Urethane (PAUt) Thin Film Composite Membrane for Improving the Reverse Osmosis Performance

by Li-Fen Liu, Xing-Ling Gu, Sa-Ren Qi, Xin Xie, Rui-Han Li, Ke Li, Chun-Yang Yu and Cong-Jie Gao

Polymers 2018, 10(4), 346; https://doi.org/10.3390/polym10040346 - 21 Mar 2018

Cited by 8 | Viewed by 5659

Abstract

In the current study, the poly (amide-urethane) (PAUt) membranes were successfully fabricated by interfacial polymerization of m-phenylenediamine (MPD) and 5-choroformyloxyisophaloyl chloride (CFIC) on the polysulfone substrates. Two modification methods based on layer-by-layer assembly were applied to modify the PAUt membrane surface to achieve [...] Read more.

In the current study, the poly (amide-urethane) (PAUt) membranes were successfully fabricated by interfacial polymerization of m-phenylenediamine (MPD) and 5-choroformyloxyisophaloyl chloride (CFIC) on the polysulfone substrates. Two modification methods based on layer-by-layer assembly were applied to modify the PAUt membrane surface to achieve antifouling property: 1. Chitosan (CS) was directly self-assembled on the PAUt membrane (i.e., PAUt-CS); and 2. polydimethyl diallyl ammonium chloride (PDDA), polystyrene sulfonate (PSS), and CS were successively self-assembled on the membrane surface (i.e., PAUt-PDDA/PSS/CS). The resultant membranes were symmetrically characterized by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Contact Angle Meter (CAM), respectively. The results indicated that the modified membranes had much smoother and more hydrophilic surfaces as compared to the nascent PAUt membrane. Meanwhile, the modified membranes exhibited better reverse osmosis performance in terms of water permeability and salt rejection. After the modified membranes were fouled by lake water, the PAUt-PDDA/PSS/CS membrane presented the best antifouling performance among the three types of membranes. Combining the reverse osmosis performance with the anti-fouling property obviously, the PAUt-PDDA/PSS/CS membrane behaved as a promising candidate to be used in real applications. Full article

(This article belongs to the Special Issue Polymerizations from Surfaces)

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12 pages, 2427 KiB

Open AccessArticle

Poly(Ionic Liquid): A New Phase in a Thermoregulated Phase Separated Catalysis and Catalyst Recycling System of Transition Metal-Mediated ATRP

by Lan Yao, Bingjie Zhang, Hongjuan Jiang, Lifen Zhang and Xiulin Zhu

Polymers 2018, 10(4), 347; https://doi.org/10.3390/polym10040347 - 21 Mar 2018

Cited by 8 | Viewed by 4463

Abstract

Poly(ionic liquid)s (PILs) have become the frontier domains in separation science because of the special properties of ionic liquids as well as their corresponding polymers. Considering their function in separation, we designed and synthesized a thermoregulated PIL. That is, this kind of PIL [...] Read more.

Poly(ionic liquid)s (PILs) have become the frontier domains in separation science because of the special properties of ionic liquids as well as their corresponding polymers. Considering their function in separation, we designed and synthesized a thermoregulated PIL. That is, this kind of PIL could separate with an organic phase which dissolves the monomers at ambient temperature. When heated to the reaction temperature, they become a homogeneous phase, and they separate again when the temperature falls to the ambient temperature after polymerization. Based on this, a thermoregulated phase separated catalysis (TPSC) system for Cu-based atom transfer radical polymerization (ATRP) was constructed. The copper catalyst (CuBr₂) used here is easily separated and recycled in situ just by changing the temperature in this system. Moreover, even when the catalyst had been recycled five times, the controllability over resultant polymers is still satisfying. Finally, only 1~2 ppm metal catalyst was left in the polymer solution phase, which indicates the really high recycling efficiency. Full article

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22 pages, 9168 KiB

Open AccessArticle

Effects of Carbon Nanotubes/Graphene Nanoplatelets Hybrid Systems on the Structure and Properties of Polyetherimide-Based Foams

by Hooman Abbasi, Marcelo Antunes and José Ignacio Velasco

Polymers 2018, 10(4), 348; https://doi.org/10.3390/polym10040348 - 21 Mar 2018

Cited by 47 | Viewed by 5440

Abstract

Foams based on polyetherimide (PEI) with carbon nanotubes (CNT) and PEI with graphene nanoplatelets (GnP) combined with CNT were prepared by water vapor induced phase separation. Prior to foaming, variable amounts of only CNT (0.1–2.0 wt %) or a combination of GnP (0.0–2.0 [...] Read more.

Foams based on polyetherimide (PEI) with carbon nanotubes (CNT) and PEI with graphene nanoplatelets (GnP) combined with CNT were prepared by water vapor induced phase separation. Prior to foaming, variable amounts of only CNT (0.1–2.0 wt %) or a combination of GnP (0.0–2.0 wt %) and CNT (0.0–2.0 wt %) for a total amount of CNT-GnP of 2.0 wt %, were dispersed in a solvent using high power sonication, added to the PEI solution, and intensively mixed. While the addition of increasingly higher amounts of only CNT led to foams with more heterogeneous cellular structures, the incorporation of GnP resulted in foams with finer and more homogeneous cellular structures. GnP in combination with CNT effectively enhanced the thermal stability of foams by delaying thermal decomposition and mechanically-reinforced PEI. The addition of 1.0 wt % GnP in combination with 1.0 wt % CNT resulted in foams with extremely high electrical conductivity, which was related to the formation of an optimum conductive network by physical contact between GnP layers and CNT, enabling their use in electrostatic discharge (ESD) and electromagnetic interference (EMI) shielding applications. The experimental electrical conductivity values of foams containing only CNT fitted well to a percolative conduction model, with a percolation threshold of 0.06 vol % (0.1 wt %) CNT. Full article

(This article belongs to the Special Issue Graphene-Polymer Composites)

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13 pages, 3520 KiB

Open AccessArticle

Photonic Molecularly Imprinted Polymer Film for the Detection of Testosterone in Aqueous Samples

by Abbas J. Kadhem, Shuting Xiang, Susan Nagel, Chung-Ho Lin and Maria Fidalgo de Cortalezzi

Polymers 2018, 10(4), 349; https://doi.org/10.3390/polym10040349 - 22 Mar 2018

Cited by 27 | Viewed by 5816

Abstract

The detection of testosterone in aqueous solutions is a difficult task due to the low concentration levels that are relevant in environmental and physiological samples. Current analytical methods are expensive and/or complex. To address this issue, we fabricated a molecularly imprinted polymer (MIP) [...] Read more.

The detection of testosterone in aqueous solutions is a difficult task due to the low concentration levels that are relevant in environmental and physiological samples. Current analytical methods are expensive and/or complex. To address this issue, we fabricated a molecularly imprinted polymer (MIP) photonic film for the detection of testosterone in water. The films were obtained using colloidal crystals as templates for the pore morphology. Monodispersed silica particles with an average diameter 330 nm were used to obtain the colloidal crystal by vertical deposition. A solution of acrylic acid with testosterone as the imprinted template was infiltrated in the colloidal crystal and polymerized via bulk polymerization; the particles were then removed by acid etching and the testosterone eluted by a suitable solvent. The material was characterized by FTIR, swelling experiments and microscopy; MIPs were investigated by equilibrium rebinding, kinetics and reuse experiments. The results showed that the MIPs exhibited selectivity to the template, a 30-min equilibration time and stability after at least six cycles of use and regeneration. After incubation, the reflectance spectra of the films showed a shift of the Bragg diffraction peak that correlated with testosterone concentration in the 5–100 ppb range. Full article

(This article belongs to the Special Issue Molecularly Imprinted Polymers)

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10 pages, 3107 KiB

Open AccessArticle

A Highly Efficient Aromatic Amine Ligand/Copper(I) Chloride Catalyst System for the Synthesis of Poly(2,6-dimethyl-1,4-phenylene ether)

by Kisoo Kim, Min Jae Shin, Yong Tae Kim, Joong-In Kim and Young Jun Kim

Polymers 2018, 10(4), 350; https://doi.org/10.3390/polym10040350 - 22 Mar 2018

Cited by 3 | Viewed by 4763

Abstract

Highly active catalyst systems for polymerizing 2,6-dimethylphenol were studied by using aromatic amine ligands and copper(I) chloride. The aromatic amine ligands employed were pyridine, 1-methylimidazole, 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine. A mixture of chloroform and methanol (9:1, v/v) was used as [...] Read more.

Highly active catalyst systems for polymerizing 2,6-dimethylphenol were studied by using aromatic amine ligands and copper(I) chloride. The aromatic amine ligands employed were pyridine, 1-methylimidazole, 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine. A mixture of chloroform and methanol (9:1, v/v) was used as a polymerization solvent. All experiments were performed with oxygen uptake measurement apparatus, while the reaction rate for each aromatic amine ligand-Cu catalyst system and the amount of by-product, 3,3′,5,5′-Tetramethyl-4,4′diphenoquinone (DPQ), were measured to determine the efficiency of the catalyst systems. The 4-aminopyridine/Cu (I) catalyst system was found to be extremely efficient in poly(2,6-dimethyl-1,4-phenylene ether) (PPE) synthesis; it had the fastest reaction rate of 6.98 × 10⁻⁴ mol/L·s and the lowest DPQ production. The relatively high basicity of 4-aminopyridne and the less steric hindrance arising from a coordination of Cu and 4-aminopyridine in this catalyst are responsible for the fast polymerization rate. When 2-aminoprydine (an isomer of 4-aminopyridine) was used as a ligand, however, no polymerization occurred probably due to steric hindrance. Full article

(This article belongs to the Special Issue Polymerization Kinetics)

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11 pages, 2498 KiB

Open AccessArticle

The Effect of Polyaniline (PANI) Coating via Dielectric-Barrier Discharge (DBD) Plasma on Conductivity and Air Drag of Polyethylene Terephthalate (PET) Yarn

by Shuai Liu, Deqi Liu and Zhijuan Pan

Polymers 2018, 10(4), 351; https://doi.org/10.3390/polym10040351 - 22 Mar 2018

Cited by 31 | Viewed by 5522

Abstract

In this paper, a simple method to prepare PANI-coated conductive PET yarn is reported, which involves pre-applying aniline and HCl vapors on PET surface and subsequent dielectric-barrier discharge (DBD) plasma treatment of the coated yarn under atmospheric pressure. The volume resistivity of the [...] Read more.

In this paper, a simple method to prepare PANI-coated conductive PET yarn is reported, which involves pre-applying aniline and HCl vapors on PET surface and subsequent dielectric-barrier discharge (DBD) plasma treatment of the coated yarn under atmospheric pressure. The volume resistivity of the optimal sample was about 1.8 × 10⁵ times lower than that of the control. Moreover, with the increase of coating amount of PANI, the air drag of PET yarns improved gradually. The surface chemistry of the treated yarn was analyzed by Fourier transform-infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), while the morphology was observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). This study offers a new method to prepare conductive fabric via air-jet loom and is expected to increase the weaving efficiency of air-jet loom. Full article

(This article belongs to the Special Issue Polymerizations from Surfaces)

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18 pages, 9651 KiB

Open AccessArticle

Novel Processing Technique to Produce Three Dimensional Polyvinyl Alcohol/Maghemite Nanofiber Scaffold Suitable for Hard Tissues

by Nor Hasrul Akhmal Ngadiman, Noordin Mohd Yusof, Ani Idris, Ehsan Fallahiarezoudar and Denni Kurniawan

Polymers 2018, 10(4), 353; https://doi.org/10.3390/polym10040353 - 22 Mar 2018

Cited by 23 | Viewed by 5050

Abstract

Fabrication of three dimensional (3D) tissue engineering scaffolds, particularly for hard tissues remains a challenge. Electrospinning has been used to fabricate scaffolds made from polymeric materials which are suitable for hard tissues. The electrospun scaffolds also have structural arrangement that mimics the natural [...] Read more.

Fabrication of three dimensional (3D) tissue engineering scaffolds, particularly for hard tissues remains a challenge. Electrospinning has been used to fabricate scaffolds made from polymeric materials which are suitable for hard tissues. The electrospun scaffolds also have structural arrangement that mimics the natural extracellular matrix. However, electrospinning has a limitation in terms of scaffold layer thickness that it can fabricate. Combining electrospinning with other processes is the way forward, and in this proposed technique, the basic shape of the scaffold is obtained by a fused deposition modelling (FDM) three dimensional (3D) printing machine using the partially hydrolysed polyvinyl alcohol (PVA) as the filament material. The 3D printed PVA becomes a template to be placed inside a mould which is then filled with the fully hydrolysed PVA/maghemite (γ-Fe₂O₃) solution. After the content in the mould solidified, the mould is opened and the content is freeze dried and immersed in water to dissolve the template. The 3D structure made of PVA/maghemite is then layered by electrospun PVA/maghemite fibers, resulting in 3D tissue engineering scaffold made from PVA/maghemite. The morphology and mechanical properties (strength and stiffness) were analysed and in vitro tests by degradation test and cell penetration were also performed. It was revealed that internally, the 3D scaffold has milli- and microporous structures whilst externally; it has a nanoporous structure as a result of the electrospun layer. The 3D scaffold has a compressive strength of 78.7 ± 0.6 MPa and a Young’s modulus of 1.43 ± 0.82 GPa, which are within the expected range for hard tissue engineering scaffolds. Initial biocompatibility tests on cell penetration revealed that the scaffold can support growth of human fibroblast cells. Overall, the proposed processing technique which combines 3D printing process, thermal inversion phase separation (TIPS) method and electrospinning process has the potential for producing hard tissue engineering 3D scaffolds. Full article

(This article belongs to the Special Issue Electrospinning of Nanofibres)

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16 pages, 3306 KiB

Open AccessArticle

Surface Modification of Wood Flour via ARGET ATRP and Its Application as Filler in Thermoplastics

by Martin Kaßel, Julia Gerke, Adrian Ley and Philipp Vana

Polymers 2018, 10(4), 354; https://doi.org/10.3390/polym10040354 - 22 Mar 2018

Cited by 7 | Viewed by 7532

Abstract

Wood flour is particularly suitable as a filler in thermoplastics because it is environmentally friendly, readily available, and offers a high strength-to-density ratio. To overcome the insufficient interfacial adhesion between hydrophilic wood and a hydrophobic matrix, a thermoplastic polymer was grafted from wood [...] Read more.

Wood flour is particularly suitable as a filler in thermoplastics because it is environmentally friendly, readily available, and offers a high strength-to-density ratio. To overcome the insufficient interfacial adhesion between hydrophilic wood and a hydrophobic matrix, a thermoplastic polymer was grafted from wood flour via surface-initiated activators regenerated by electron transfer-atom transfer radical polymerization (SI-ARGET ATRP). Wood particles were modified with an ATRP initiator and subsequently grafted with methyl acrylate for different polymerization times in the absence of a sacrificial initiator. The successful grafting of poly(methyl acrylate) (PMA) was demonstrated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and water contact angle (WCA) measurements. To confirm the control over the polymerization, a cleavable ATRP initiator was immobilized on the particles, allowing the detachment of the grafted polymer under mild conditions. The grafted particles were incorporated into a PMA matrix using solvent casting and their influence on the mechanical properties (Young’s modulus, yield strength, and toughness) of the composite was investigated. Tensile testing showed that the mechanical properties improved with increasing polymerization time and increasing ratio of incorporated grafted particles. Full article

(This article belongs to the Special Issue Polymerizations from Surfaces)

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14 pages, 18462 KiB

Open AccessArticle

Investigation and Characterization of Plasma-Treated Poly(3-hydroxybutyrate) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopolymers for an In Vitro Cellular Study of Mouse Adipose-Derived Stem Cells

by Chih-Kai Chang, Hui-Min David Wang and John Chi-Wei Lan

Polymers 2018, 10(4), 355; https://doi.org/10.3390/polym10040355 - 22 Mar 2018

Cited by 24 | Viewed by 5775

Abstract

Polyhydroxyalkanoates (PHAs) are a type of thermoprocessable and biodegradable polyester, which represent a potential sustainable replacement for fossil-fuel synthetic polymers, such as polypropylene and polyethylene. In recent years, copolymers of PHAs, i.e., poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), have received attention for [...] Read more.

Polyhydroxyalkanoates (PHAs) are a type of thermoprocessable and biodegradable polyester, which represent a potential sustainable replacement for fossil-fuel synthetic polymers, such as polypropylene and polyethylene. In recent years, copolymers of PHAs, i.e., poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), have received attention for medical and packaging industrial applications, due to their biodegradable, toxic-free, and biocompatible nature. This study investigated and characterized plasma-treated PHB and PHBV films fermented with Ralstonia eutropha H16. The X-ray photoelectron spectroscopy (XPS) and water contact angle analyses on the plasma-treated PHB and PHBV film surfaces revealed an increase in the number of functional groups and contact angle degree, respectively, compared to that of the untreated films. In addition, an in vitro experiment of mouse adipose-derived stem cells showed better growth and adhesion of the cells on the surface of plasma-treated PHBV film. Overall, these results reveal that plasma surface modifications are useful in biomaterial development. Full article

(This article belongs to the Special Issue Biodegradable and Biobased Polyesters)

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23 pages, 39807 KiB

Open AccessArticle

Flexible Adhesive in Composite-to-Brick Strengthening—Experimental and Numerical Study

by Arkadiusz Kwiecień, Piotr Krajewski, Łukasz Hojdys, Marcin Tekieli and Marek Słoński

Polymers 2018, 10(4), 356; https://doi.org/10.3390/polym10040356 - 22 Mar 2018

Cited by 22 | Viewed by 5184

Abstract

This paper investigates composite-to-brick strengthening systems with flexible adhesive made of polyurethane (Carbon Fibre Reinforced Polyurethane (CFRPU) and Steel Reinforced Polyurethane (SRPU)) and epoxy resin (Carbon Fibre Reinforced Polymer (CFRP) and Steel Reinforced Polymer (SRP). The specimens were tested in a single lap [...] Read more.

This paper investigates composite-to-brick strengthening systems with flexible adhesive made of polyurethane (Carbon Fibre Reinforced Polyurethane (CFRPU) and Steel Reinforced Polyurethane (SRPU)) and epoxy resin (Carbon Fibre Reinforced Polymer (CFRP) and Steel Reinforced Polymer (SRP). The specimens were tested in a single lap shear test (SLST). LVDT displacement transducers (LVDT – Linear Variable Differential Transformer) and digital image correlation method (DIC) based measurement systems were used to measure displacements and strains. The obtained results were applied in a numerical analysis of the 3D model of the SLST specimen, with flexible adhesives modeled as a hyper-elastic model. The DIC and LVDT based systems demonstrated a good correlation. Experimental and numerical analysis confirmed that composite-to-brick strengthening systems with flexible adhesives are more effective on brittle substrates than stiff ones, as they are able to reduce stress concentrations and more evenly distribute stress along the entire bonded length, thus having a higher load carrying capacity. Full article

(This article belongs to the Special Issue Selected Papers from "SMAR 2017")

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11 pages, 29704 KiB

Open AccessArticle

Phase Transition Effects on Mechanical Properties of NIPA Hydrogel

by Ni Zhang, Shoujing Zheng, Zhouzhou Pan and Zishun Liu

Polymers 2018, 10(4), 358; https://doi.org/10.3390/polym10040358 - 23 Mar 2018

Cited by 17 | Viewed by 4279

Abstract

Due to its excellent temperature sensitivity, the Poly(N-isopropylacrylamide) (NIPA) hydrogel has attracted great interest for a wide variety of applications in tissue engineering and regenerative medicine. NIPA hydrogel undergoes an abrupt volume phase transition at a lower critical solution temperature (LCST) [...] Read more.

Due to its excellent temperature sensitivity, the Poly(N-isopropylacrylamide) (NIPA) hydrogel has attracted great interest for a wide variety of applications in tissue engineering and regenerative medicine. NIPA hydrogel undergoes an abrupt volume phase transition at a lower critical solution temperature (LCST) of 30–35 °C. However, the mechanical behaviors of NIPA hydrogel induced by phase transition are still not well understood. In this study, phase transition effects on mechanical properties of NIPA hydrogel are quantitatively studied from experimental studies. The mechanical properties of NIPA hydrogel with the LSCT around 35 °C are systemically studied with varying temperatures (31–39 °C) under a tensile test. We find that the mechanical properties of NIPA hydrogel are greatly influenced by phase transition during the tension process. The maximum nominal stress and maximum stretch above the LCST are larger than those of below the LCST. The Young’s modulus of NIPA hydrogel is around 13 kPa at 31 °C and approximately 28 kPa at 39 °C. A dramatic increase of Young’s modulus values is observed as the temperature increases through the phase transition. The samples at a temperature around the LCST are easy to rupture, because of phase coexistent. Additionally, NIPA hydrogel displays toughening behavior under a cyclic load. Furthermore, the toughening characteristic is different between the swollen state and the collapsed state. This might originate from the internal fracture process and redistribution of polymer chains during the tension process. Full article

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13 pages, 12351 KiB

Open AccessArticle

Thermal, Structural, and Rheological Characterization of Waxy Starch as a Cryogel for Its Application in Food Processing

by Jonathan Coria-Hernández, Abraham Méndez-Albores, Rosalía Meléndez-Pérez, Marta Elvia Rosas-Mendoza and José Luis Arjona-Román

Polymers 2018, 10(4), 359; https://doi.org/10.3390/polym10040359 - 23 Mar 2018

Cited by 12 | Viewed by 4180

Abstract

Starch is the major component of cereal, pulses, and root crops. Starch consists of two kinds of glucose polymers, amylose and amylopectin. Waxy starch—with 99–100% amylopectin—has distinctive properties, which define its functionality in many food applications. In this research, a novel material was [...] Read more.

Starch is the major component of cereal, pulses, and root crops. Starch consists of two kinds of glucose polymers, amylose and amylopectin. Waxy starch—with 99–100% amylopectin—has distinctive properties, which define its functionality in many food applications. In this research, a novel material was prepared through the cryogelification of waxy starch (WS) using four cycles of freezing and thawing in indirect contact with liquid nitrogen at −150 °C. Polyvinyl alcohol (PVA) was used as a reference. The cryogels were characterized using several validation methodologies: modulated differential scanning calorimetry (MDSC), scanning electron microscopy (SEM), rheology, and Fourier transform infrared (FTIR) spectroscopy with diffuse reflectance (DR). Based on the number of freeze–thaw cycles, significant changes were found (P < 0.05) showing important structural modifications as well as reorganization of the polymeric matrix. Two cryogelification cycles of the WS were enough to obtain the best structural and functional characteristics, similar to those of PVA, which has already been tested as a cryogel. From these results, it is concluded that WS has potential as a cryogel for application in food processing. Full article

(This article belongs to the Collection Polysaccharides)

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13 pages, 7452 KiB

Open AccessArticle

Structural Transformations of Amino-Acid-Based Polymers: Syntheses and Structural Characterization

by Tien-Wen Tseng, Tzuoo-Tsair Luo, Hsiao-Shan Chiu, Chih-Chieh Wang, Gene-Hsiang Lee, Hwo-Shuenn Sheu and Kuang-Lieh Lu

Polymers 2018, 10(4), 360; https://doi.org/10.3390/polym10040360 - 23 Mar 2018

Cited by 3 | Viewed by 3715

Abstract

A discrete complex [Zn(tpro)₂(H₂O)₂] (1, Htpro = l-thioproline), and two structural isomers of coordination polymers, a 1D chain of [Zn(tpro)₂]_n (2) and a layered structure [Zn(tpro)₂]_n [...] Read more.

A discrete complex [Zn(tpro)₂(H₂O)₂] (1, Htpro = l-thioproline), and two structural isomers of coordination polymers, a 1D chain of [Zn(tpro)₂]_n (2) and a layered structure [Zn(tpro)₂]_n (3), were synthesized and characterized. The discrete complex 1 undergoes a temperature-driven structural transformation, leading to the formation of a 1D helical coordination polymer 2. Compound 3 is comprised of a 2D homochiral layer network with a (4,4) topology. These layers are mutually linked through hydrogen bonding interactions, resulting in the formation of a 3D network. When 1 is heated, it undergoes nearly complete conversion to the microcrystalline form, i.e., compound 2, which was confirmed by powder X-ray diffractions (PXRD). The carboxylate motifs could be activated after removing the coordinated water molecules by heating at temperatures of up to 150 °C, their orientations becoming distorted, after which, they attacked the activation sites of the Zn(II) centers, leading to the formation of a 1D helix. Moreover, a portion of the PXRD pattern of 1 was converted into the patterns corresponding to 2 and 3, and the ratio between 2 and 3 was precisely determined by the simulation study of in-situ synchrotron PXRD expriments. Consequently, such a 0D complex is capable of underdoing structural transformations and can be converted into 1D and/or 2D amino acid-based coordination polymers. Full article

(This article belongs to the Special Issue Coordination Polymer)

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20 pages, 35123 KiB

Open AccessArticle

Comparative Analysis of Existing RC Columns Jacketed with CFRP or FRCC

by Marta Del Zoppo, Marco Di Ludovico, Alberto Balsamo and Andrea Prota

Polymers 2018, 10(4), 361; https://doi.org/10.3390/polym10040361 - 24 Mar 2018

Cited by 44 | Viewed by 5512

Abstract

Reinforced concrete (RC) columns typical of existing structures often exhibit premature failures during seismic events (i.e., longitudinal bars buckling and shear interaction mechanisms) due to the poor quality concrete and the absence of proper seismic details in the potential plastic hinge region. The [...] Read more.

Reinforced concrete (RC) columns typical of existing structures often exhibit premature failures during seismic events (i.e., longitudinal bars buckling and shear interaction mechanisms) due to the poor quality concrete and the absence of proper seismic details in the potential plastic hinge region. The Fiber Reinforced Polymers (FRP) externally bonded reinforcement is known to be a valid technique to improve the shear capacity or the ductility of existing RC columns. However, few experimental tests have proven its effectiveness in the case of columns affected by shear interaction mechanisms. In this work, the behavior of existing RC columns with border line behavior between flexure and shear have been investigated in the case of poor quality concrete and light FRP strengthening with local jacketing and medium quality concrete and strong FRP strengthening with local jacketing, in order to highlight the effect of concrete strength on the effectiveness of the retrofit intervention. As an alternative to FRP jacketing; the effectiveness of the Fiber Reinforced Cementitious Composite (FRCC) jacketing for the seismic strengthening of columns with highly deteriorated concrete cover or columns already damaged by an earthquake is also evaluated. Six full-scale RC columns have been tested under cyclic loading: one was used as a control specimen; four were strengthened in the potential plastic hinge region with carbon FRP (CFRP); and one was fully jacketed with FRCC. The comparison between poor and medium quality concrete columns showed that the CFRP local jacketing is more effective in the case of poor quality concrete. The FRCC jacketing appears to be a sound repair strategy and a suitable alternative to the FRP jacketing in case of poor quality; however, more experimental research is needed for improving this retrofit technique. Full article

(This article belongs to the Special Issue Selected Papers from "SMAR 2017")

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14 pages, 4898 KiB

Open AccessArticle

Unsaturated Polyester Resin Nanocomposites Containing ZnO Modified with Oleic Acid Activated by N,N′-Carbonyldiimidazole

by Hengzhi Chen, Xiaoxue Tian and Jing Liu

Polymers 2018, 10(4), 362; https://doi.org/10.3390/polym10040362 - 24 Mar 2018

Cited by 19 | Viewed by 6210

Abstract

Hydrophobic zinc oxide (ZnO) nanoparticles were produced through grafting aminopropyltriethoxysilane (APS) and oleic acid (OA), which was activated by N,N′-carbonyldiimidazole (CDI). The functional group containing ZnO nanoparticles were incorporated into unsaturated polyester (UP) resin, and their dispersibility in the UP [...] Read more.

Hydrophobic zinc oxide (ZnO) nanoparticles were produced through grafting aminopropyltriethoxysilane (APS) and oleic acid (OA), which was activated by N,N′-carbonyldiimidazole (CDI). The functional group containing ZnO nanoparticles were incorporated into unsaturated polyester (UP) resin, and their dispersibility in the UP matrix and effects on the properties of UP/ZnO nanocomposites were investigated. ZnO nanoparticles modified by APS and OA activated by CDI, (CDI–OA–APS–ZnO), can be homogeneously dispersed as supported by transmission electron microscopy (TEM) investigations and had been encapsulated in the UP resin. CDI–OA–APS–ZnO nanoparticles were embedded in the net structure of the UP composites through chemical bonds between oleic acid, styrene, and polyester resin, which significantly influence the cure reaction of UP resin and the properties of UP composites. Thermogravimetric analysis (TGA) results show that the incorporation of ZnO nanoparticles could improve the thermal stability of UP when thermal cracking temperature exceeds 365 °C. The exothermic peak and the initial temperature of cure reaction of the UP resin decreased with increasing ZnO content. The tensile strength and bending strength of UP/CDI–OA–APS–ZnO nanocomposites increased by 91.4% and 71.3% when 3 wt % CDI–OA–APS–ZnO nanoparticles was added into the composites, respectively, compared with pure UP resin. Full article

(This article belongs to the Special Issue Polymer Hybrids and Composites)

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11 pages, 17800 KiB

Open AccessArticle

Effect of Counterion Valence on Conformational Behavior of Spherical Polyelectrolyte Brushes Confined between Two Parallel Walls

by Lujuan Li, Qianqian Cao and Chuncheng Zuo

Polymers 2018, 10(4), 363; https://doi.org/10.3390/polym10040363 - 24 Mar 2018

Cited by 3 | Viewed by 3380

Abstract

We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. [...] Read more.

We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. For the monovalent case, the increase of the charge fraction leads to extended brush conformation for different slit width (distance between two walls) but collapsed brush in the presence of trivalent counterions is observed. The confinement does not affect electrostatic correlation between trivalent counterions and charged monomers. However, it was found that narrow slit width contributes to stronger electrostatic correlation for the monovalent case. This is because more monovalent counterions are inside the brush at strong confinement, but almost all trivalent counterions are trapped into the brush independently of the slit width. The diffusion of counterions under the confinement is related to the electrostatic correlation. Our simulations also reveal that the brush thickness depends on the slit width nonlinearly. Full article

(This article belongs to the Collection Polyelectrolytes)

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12 pages, 23781 KiB

Open AccessArticle

Aligned P(VDF-TrFE) Nanofibers for Enhanced Piezoelectric Directional Strain Sensing

by Yonggang Jiang, Longlong Gong, Xiaohe Hu, Yong Zhao, Huawei Chen, Lin Feng and Deyuan Zhang

Polymers 2018, 10(4), 364; https://doi.org/10.3390/polym10040364 - 25 Mar 2018

Cited by 50 | Viewed by 10338

Abstract

Piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) nanofibers fabricated by electrospinning have drawn increasing levels of attention in the fields of flexible sensors and nanogenerators. However, the directional dependence of piezoelectricity of electrospun nanofibers remains elusive. In this study, the piezoelectric performances of individual nanofibers are [...] Read more.

Piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) nanofibers fabricated by electrospinning have drawn increasing levels of attention in the fields of flexible sensors and nanogenerators. However, the directional dependence of piezoelectricity of electrospun nanofibers remains elusive. In this study, the piezoelectric performances of individual nanofibers are characterized by piezoresponse force microscopy (PFM), while the effects of annealing on β-phase crystallinities are investigated by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The experimental results reveal that the as-spun P(VDF-TrFE) nanofibers form higher content of β-phase compared with spin-coated films, and the content of β-phase increases by annealing. The annealed P(VDF-TrFE) nanofiber exhibits distinct vertical polarization switching characteristics. The high piezoelectric output in the thickness direction and low piezoelectric output in the longitudinal direction of the nanofiber mats further confirm that the preferential dipole orientation of electrospun P(VDF-TrFE) nanofibers is normal to the surface of the substrate. Highly aligned P(VDF-TrFE) nanofibers show directional strain sensing ability due to the piezoelectric and mechanical anisotropy. Full article

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17 pages, 50192 KiB

Open AccessArticle

Nucleating and Plasticization Effects in Drawn Poly(Lactic Acid) Fiber during Accelerated Weathering Degradation

by Masakazu Nishida, Tomoko Tanaka, Toshiyuki Tanaka and Yoshio Hayakawa

Polymers 2018, 10(4), 365; https://doi.org/10.3390/polym10040365 - 25 Mar 2018

Cited by 13 | Viewed by 4653

Abstract

Changes in the polymer properties of poly(lactic acid) (PLA) fibers during drawing and degradation processes were analyzed using solid-state NMR, with the goal of elucidating morphological changes that influence fiber tensile properties. Combination of X-ray diffraction (XRD) and differential scanning calorimeter (DSC) indicated [...] Read more.

Changes in the polymer properties of poly(lactic acid) (PLA) fibers during drawing and degradation processes were analyzed using solid-state NMR, with the goal of elucidating morphological changes that influence fiber tensile properties. Combination of X-ray diffraction (XRD) and differential scanning calorimeter (DSC) indicated that the drawn PLA fibers consisted of different proportions of α crystalline and amorphous forms. ¹³C CP-MAS NMR spectra showed amorphous-like broad singlet signals, of which the full width at half maximum (FWHM) decreased with increasing crystallinity and crystal orientation. The T₁H value decreased by interaction with additives and increased with increasing crystal orientation. The interaction with additives also reduced T₁C values, which increased with increasing crystallinity. Use of organic clay enhanced the crystallization of high draw-ratio PLA fibers due to nucleation, which increased tensile strength; this effect gradually decreased with time during accelerated weathering. In contrast, the plasticization due to the addition of flexible polymers increased fiber elongation, which rapidly dropped during the degradation. Changes of FWHM, T₁H, and T₁C values indicated that the degradation occurred at sites within the amorphous portions of the PLA fibers containing organic clay, while the flexible polymers were preferentially degraded if they were present in the PLA fibers. Full article

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17 pages, 28628 KiB

Open AccessArticle

Transport Asymmetry of Novel Bi-Layer Hybrid Perfluorinated Membranes on the Base of MF-4SC Modified by Halloysite Nanotubes with Platinum

by Anatoly Filippov, Daria Petrova, Irina Falina, Natalia Kononenko, Evgenii Ivanov, Yuri Lvov and Vladimir Vinokurov

Polymers 2018, 10(4), 366; https://doi.org/10.3390/polym10040366 - 25 Mar 2018

Cited by 20 | Viewed by 4128

Abstract

Three types of bi-layer hybrid nanocomposites on the base of perfluorinated cation-exchange membrane MF-4SC (Russian analogue of Nafion^®-117) were synthesized and characterized. It was found that two membranes possess the noticeable asymmetry of the current–voltage curve (CVC) under changing their orientation [...] Read more.

Three types of bi-layer hybrid nanocomposites on the base of perfluorinated cation-exchange membrane MF-4SC (Russian analogue of Nafion^®-117) were synthesized and characterized. It was found that two membranes possess the noticeable asymmetry of the current–voltage curve (CVC) under changing their orientation towards the applied electric field, despite the absence of asymmetry of diffusion permeability. These phenomena were explained in the frame of the “fine-porous model” expanded for bi-layer membranes. A special procedure to calculate the real values of the diffusion layers thickness and the limiting current density was proposed. Due to asymmetry effects of the current voltage curves of bi-layer hybrid membranes on the base of MF-4SC, halloysite nanotubes and platinum nanoparticles, it is prospective to assemble membrane switches (membrane relays or diodes) with predictable transport properties, founded upon the theory developed here. Full article

(This article belongs to the Special Issue Selected Papers from "ECIS 2017")

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18 pages, 18321 KiB

Open AccessArticle

Sorption of Hg(II) and Pb(II) Ions on Chitosan-Iron(III) from Aqueous Solutions: Single and Binary Systems

by Byron Lapo, Hary Demey, Jessenia Zapata, Cristhian Romero and Ana María Sastre

Polymers 2018, 10(4), 367; https://doi.org/10.3390/polym10040367 - 25 Mar 2018

Cited by 34 | Viewed by 5669

Abstract

The present work describes the study of mercury Hg(II) and lead Pb(II) removal in single and binary component systems into easily prepared chitosan-iron(III) bio-composite beads. Scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and point [...] Read more.

The present work describes the study of mercury Hg(II) and lead Pb(II) removal in single and binary component systems into easily prepared chitosan-iron(III) bio-composite beads. Scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and point of zero charge (pH_pzc) analysis were carried out. The experimental set covered pH study, single and competitive equilibrium, kinetics, chloride and sulfate effects as well as sorption–desorption cycles. In single systems, the Langmuir nonlinear model fitted the experimental data better than the Freundlich and Sips equations. The sorbent material has more affinity to Hg(II) rather than Pb(II) ions, the maximum sorption capacities were 1.8 mmol·g⁻¹ and 0.56 mmol·g⁻¹ for Hg(II) and Pb(II), respectively. The binary systems data were adjusted with competitive Langmuir isotherm model. The presence of sulfate ions in the multicomponent system [Hg(II)-Pb(II)] had a lesser impact on the sorption efficiency than did chloride ions, however, the presence of chloride ions improves the selectivity towards Hg(II) ions. The bio-based material showed good recovery performance of metal ions along three sorption–desorption cycles. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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8 pages, 869 KiB

Open AccessCommunication

Molecular Design of Soluble Biopolyimide with High Rigidity

by Sumant Dwivedi and Tatsuo Kaneko

Polymers 2018, 10(4), 368; https://doi.org/10.3390/polym10040368 - 26 Mar 2018

Cited by 9 | Viewed by 5412

Abstract

New soluble biopolyimides were prepared from a diamine derived from an exotic amino acid (4-aminocinnamic acid) with several kinds of tetracarboxylic dianhydride. The biopolyimide molecular structural flexibility was tailored by modifying the tetracarboxylic dianhydride moiety. The obtained polyimides were soluble in various solvents [...] Read more.

New soluble biopolyimides were prepared from a diamine derived from an exotic amino acid (4-aminocinnamic acid) with several kinds of tetracarboxylic dianhydride. The biopolyimide molecular structural flexibility was tailored by modifying the tetracarboxylic dianhydride moiety. The obtained polyimides were soluble in various solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, and even tetrahydrofuran. It was observed that the biopolyimide solubility was greatly dependent upon the structural flexibility (torsion energy). Flexible structure facilitated greater solubility. The synthesized biopolyimides were largely amorphous and had number-average molecular weight (M_n) in the range (5–8) × 10⁵. The glass transition temperatures (T_g) of the polymers ranged from 259–294 °C. These polymers exhibited good thermal stability without significant weight loss up to 410 °C. The temperatures at 10% weight loss (T_d10) for synthesized biopolyimide ranged from 375–397 °C. Full article

(This article belongs to the Special Issue Aromatic Polymers)

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11 pages, 13667 KiB

Open AccessArticle

POSS Dental Nanocomposite Resin: Synthesis, Shrinkage, Double Bond Conversion, Hardness, and Resistance Properties

by Yizhi Liu, Xiaorong Wu, Yi Sun and Weili Xie

Polymers 2018, 10(4), 369; https://doi.org/10.3390/polym10040369 - 26 Mar 2018

Cited by 29 | Viewed by 5244

Abstract

Nanocomposite dental resins with 0, 2, 5, and 10 wt % methacryl polyhedral oligomeric silsesquioxane (POSS) as filler in the resin matrix were prepared by a light curing method.The atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), nanoindentation, and nanoscratch tests were [...] Read more.

Nanocomposite dental resins with 0, 2, 5, and 10 wt % methacryl polyhedral oligomeric silsesquioxane (POSS) as filler in the resin matrix were prepared by a light curing method.The atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), nanoindentation, and nanoscratch tests were carried out to study the effect of POSS contents on the compatibility, double bond conversion, volumetric shrinkage, hardness, modulus, and resistance of the dental resins. POSS was very uniformly dispersed and showed a good compatibility with the matrix. The double bond conversion increased and the volume reduced with the addition of POSS. As the POSS addition increased, the mechanical properties increased initially. Small addition of POSS remarkably enhanced the hardness and scratch resistance of the resin matrix. Full article

(This article belongs to the Special Issue Siloxane-Based Polymers)

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12 pages, 9472 KiB

Open AccessArticle

A Study on Mechanical Characteristics of Phosphor Film Containing Methyl Silicone Resin Based on Crosslinking Reaction Analysis

by Jeong Yeon Park, Young Bae Ko, Moonwoo La and Gil Sang Yoon

Polymers 2018, 10(4), 370; https://doi.org/10.3390/polym10040370 - 26 Mar 2018

Viewed by 3730

Abstract

This study reveals a methodological research for predicting mechanical properties of phosphor films through the chemical crosslinking reaction of methyl silicone resin during fabrication of the phosphor films. Crosslinking point according to the type of methyl silicone resins was verified through the magnitude [...] Read more.

This study reveals a methodological research for predicting mechanical properties of phosphor films through the chemical crosslinking reaction of methyl silicone resin during fabrication of the phosphor films. Crosslinking point according to the type of methyl silicone resins was verified through the magnitude of the absorption peak of the functional group and the curing reaction heat. Then, we measured mechanical properties of the fabricated phosphor films. As a result, it was figured out that the number of the crosslinking point was directly proportional to the total curing reaction heat, and also affected the mechanical properties of the phosphor films. Based on the correlation of curing reaction heat and crosslinking point of the methyl silicone resins and mechanical properties of the fabricated phosphor films, we proposed a methodology that can understand and control the phosphor films in advance of finishing the fabrication of the final phosphor products. Full article

(This article belongs to the Collection Silicon-Containing Polymeric Materials)

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16 pages, 19757 KiB

Open AccessArticle

Mg(II) Coordination Polymers Based on Flexible Isomeric Tetracarboxylate Ligands: Syntheses, Structures, Structural Transformation and Luminescent Properties

by Kedar Bahadur Thapa, Xiang-Kai Yang and Jhy-Der Chen

Polymers 2018, 10(4), 371; https://doi.org/10.3390/polym10040371 - 26 Mar 2018

Cited by 7 | Viewed by 5874

Abstract

By using a new flexible tetracarboxylic acid, bis(3,5-dicarboxyphenyl) adipoamide, H₄L¹, and its isomer, bis(2,5-dicarboxyphenyl)adipoamide, H₄L², three Mg(II) coordination polymers, {[Mg₂(L¹)(H₂O)₂]·2EtOH·3H₂O}_n, 1, [...] Read more.

By using a new flexible tetracarboxylic acid, bis(3,5-dicarboxyphenyl) adipoamide, H₄L¹, and its isomer, bis(2,5-dicarboxyphenyl)adipoamide, H₄L², three Mg(II) coordination polymers, {[Mg₂(L¹)(H₂O)₂]·2EtOH·3H₂O}_n, 1, [Mg₂(L¹)(H₂O)₈]_n, 2, and {[Mg₂(L²)(H₂O)₆]·H₂O}_n, 3, have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 are the solvent ratio-dependent hydrothermally stable products. The tetracarboxylate ligand of complex 1 connects eight Mg(II) ions through nine oxygen atoms, resulting in a three-dimensional (3D) 5-connected uninodal net with a rare non-interpenetrating (4⁴.6⁶)-pcu-5-Pmna topology, whereas those of 2 and 3 link four Mg(II) ions through four oxygen atoms and six Mg(II) ions through six oxygen atoms, forming a 1D linear chain and a 3,6-connected 2-nodal 3D net having {4.6²}₂{4².6¹⁰.8³}-rtl topology, respectively. Complex 1 shows a series of structural transformations on heating to 200 °C and almost reversible structural transformation when the activated products were immersed in a mixture of ethanol and water or on hydrothermal. Likewise, complex 2 exhibits a reversible structural transformation on heating/hydrothermal, while 3 exhibits irreversible structural transformations. All three complexes exhibit blue light emissions, with that of complex 3 being much more intense. Full article

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11 pages, 2801 KiB

Open AccessArticle

Fluorescent Labeling of Polysaccharides from Masson Pine Pollen and Its Effect on RAW264.7 Macrophages

by Mengmeng Sun, Fangchen Su, Jinxin Yang, Zheng Gao and Yue Geng

Polymers 2018, 10(4), 372; https://doi.org/10.3390/polym10040372 - 26 Mar 2018

Cited by 16 | Viewed by 7672

Abstract

In order to explore the immediate effect of polysaccharides and macrophages, polysaccharides from masson pine pollen (PPM60) were labeled with fluorescein isothiocyanate (FITC) by using a chemical-derived method, and the reactant was named PPM60-Tyr-FITC. Direct interaction of PPM60-Tyr-FITC and RAW264.7 macrophages could be [...] Read more.

In order to explore the immediate effect of polysaccharides and macrophages, polysaccharides from masson pine pollen (PPM60) were labeled with fluorescein isothiocyanate (FITC) by using a chemical-derived method, and the reactant was named PPM60-Tyr-FITC. Direct interaction of PPM60-Tyr-FITC and RAW264.7 macrophages could be detected by flow cytometer (FCM), and this interaction could be inhibited by Pitstop 2 (clathrin inhibitor) and TAK-242 (Toll-like receptor 4 inhibitor). The results of confocal laser scanning microscopy (CLSM) also revealed that there was a co-localization phenomenon between PPM60-Tyr-FITC and RAW264.7 macrophage receptors, and it could be suppressed by Pitstop 2 and TAK-242. It was confirmed that PPM60 enters into RAW264.7 macrophages mainly through endocytosis, rather than the phagocytosis, and TLR4 played a mediating role. Full article

(This article belongs to the Special Issue Polysaccharides)

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18 pages, 7200 KiB

Open AccessArticle

Mechanical Measurement System and Precision Analysis for Tactile Property Evaluation of Porous Polymeric Materials

by Bao-Guo Yao, Yun-Liang Peng and Yun-Juan Yang

Polymers 2018, 10(4), 373; https://doi.org/10.3390/polym10040373 - 27 Mar 2018

Cited by 7 | Viewed by 5218

Abstract

Tactile properties are one of the most important attributes of porous polymeric materials such as textiles, comprising a subjective evaluation index for textile materials and functional clothing, primarily affecting the sensation of comfort during the wearing of a garment. A new test method [...] Read more.

Tactile properties are one of the most important attributes of porous polymeric materials such as textiles, comprising a subjective evaluation index for textile materials and functional clothing, primarily affecting the sensation of comfort during the wearing of a garment. A new test method was proposed, and a mechanical measurement system was developed to objectively characterize the tactile properties of porous polymeric materials by simulating the dynamic contact processes during human skin contact with the materials and in consideration of different aspects of tactile sensations. The measurement system can measure the bending, compression, friction, and thermal transfer properties in one apparatus, and is capable of associating the objective measurements with the subjective tactile sensations. The test and evaluation method, the components of the mechanical measurement system, the definition and grading method of the evaluation indices, and the neural network prediction model from objective test results to subjective sensations of tactile properties were presented. The experiments were conducted for the objective tests and correlation tests. Seven types of porous polymeric sheet materials from seven categories for the tactile properties were cut to a size of 200 mm × 200 mm and tested. Each index of tactile properties was significantly different (P < 0.05) between different sheet materials. The correlations of bending, compression, friction, and thermal transfer properties with Kawabata KES test methods were analyzed. An intra-laboratory test was conducted and an analysis of the variance was performed to determine the critical differences of within laboratory precisions of the measurement system. This mechanical measurement system provides a method and system for objective measurement and evaluation of tactile properties of porous polymeric sheet materials in industrial application. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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15 pages, 62321 KiB

Open AccessArticle

Finite Element Analysis of Three-Dimensional (3D) Auxetic Textile Composite under Compression

by Jifang Zeng and Hong Hu

Polymers 2018, 10(4), 374; https://doi.org/10.3390/polym10040374 - 27 Mar 2018

Cited by 5 | Viewed by 5369

Abstract

This paper reports a finite element (FE) analysis of three-dimensional (3D) auxetic textile composite by using commercial software ANSYS 15 under compression. The two-dimensional (2D) FE model was first developed and validated by experiment. Then, the validated model was used to evaluate effects [...] Read more.

This paper reports a finite element (FE) analysis of three-dimensional (3D) auxetic textile composite by using commercial software ANSYS 15 under compression. The two-dimensional (2D) FE model was first developed and validated by experiment. Then, the validated model was used to evaluate effects of structural parameters and constituent material properties. For the comparison, 3D non-auxetic composite that was made with the same constituent materials and structural parameters, but with different yarn arrangement in the textile structure was also analyzed at the same time. The analysis results showed that the auxetic and non-auxetic composites have different compression behaviors and the auxetic composite has better the energy absorption capacity than the non-auxetic composite under the same compression stress. The study has provided us a guidance to design and fabricate auxetic composites with the required mechanical behavior by appropriately selecting structural parameters and constituent materials. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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14 pages, 25431 KiB

Open AccessArticle

Fabrication of Stretchable Copper Coated Carbon Nanotube Conductor for Non-Enzymatic Glucose Detection Electrode with Low Detection Limit and Selectivity

by Dawei Jiang, Zhongsheng Liu, Kunkun Wu, Linlin Mou, Raquel Ovalle-Robles, Kanzan Inoue, Yu Zhang, Ningyi Yuan, Jianning Ding, Jianhua Qiu, Yi Huang and Zunfeng Liu

Polymers 2018, 10(4), 375; https://doi.org/10.3390/polym10040375 - 28 Mar 2018

Cited by 13 | Viewed by 6598

Abstract

The increasing demand for wearable glucose sensing has stimulated growing interest in stretchable electrodes. The development of the electrode materials having large stretchability, low detection limit, and good selectivity is the key component for constructing high performance wearable glucose sensors. In this work, [...] Read more.

The increasing demand for wearable glucose sensing has stimulated growing interest in stretchable electrodes. The development of the electrode materials having large stretchability, low detection limit, and good selectivity is the key component for constructing high performance wearable glucose sensors. In this work, we presented fabrication of stretchable conductor based on the copper coated carbon nanotube sheath-core fiber, and its application as non-enzymatic electrode for glucose detection with high stretchability, low detection limit, and selectivity. The sheath-core fiber was fabricated by coating copper coated carbon nanotube on a pre-stretched rubber fiber core followed by release of pre-stretch, which had a hierarchically buckled structure. It showed a small resistance change as low as 27% as strain increasing from 0% to 500% strain, and a low resistance of 0.4 Ω·cm⁻¹ at strain of 500%. This electrode showed linear glucose concentration detection in the range between 0.05 mM and 5 mM and good selectivity against sucrose, lactic acid, uric acid, acrylic acid in phosphate buffer saline solution, and showed stable signal in high salt concentration. The limit of detection (LOD) was 0.05 mM, for the range of 0.05–5 mM, the sensitivity is 46 mA·M⁻¹. This electrode can withstand large strain of up to 60% with negligible influence on its performance. Full article

(This article belongs to the Special Issue Soft Materials and Systems)

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17 pages, 13691 KiB

Open AccessArticle

Polymerization-Driven Immobilization of dc-APGD Synthesized Gold Nanoparticles into a Quaternary Ammonium-Based Hydrogel Resulting in a Polymeric Nanocomposite with Heat-Transfer Applications

by Piotr Cyganowski, Anna Dzimitrowicz, Piotr Jamroz, Dorota Jermakowicz-Bartkowiak and Pawel Pohl

Polymers 2018, 10(4), 377; https://doi.org/10.3390/polym10040377 - 29 Mar 2018

Cited by 10 | Viewed by 4136

Abstract

A new method for the production of nanocomposites, composed of gold nanoparticles (AuNPs) and (vinylbenzyl)trimethylammonium chloride-co-N,N-methylene bisacrylamide (VBTAC-co-MBA) hydrogel, is described. Raw-AuNPs of defined optical and granulometric properties were synthesized using direct current atmospheric pressure [...] Read more.

A new method for the production of nanocomposites, composed of gold nanoparticles (AuNPs) and (vinylbenzyl)trimethylammonium chloride-co-N,N-methylene bisacrylamide (VBTAC-co-MBA) hydrogel, is described. Raw-AuNPs of defined optical and granulometric properties were synthesized using direct current atmospheric pressure glow discharge (dc-APGD) generated in contact with a solution of HAuCl₄. Different approaches to the polymerization-driven synthesis of Au/VBTAC-co-MBA nanocomposites were tested. It was established that homogenous dispersion of AuNPs in this new nanomaterial with was achieved in the presence of NaOH in the reaction mixture. The new nanocomposite was found to have excellent heat-transfer properties. Full article

(This article belongs to the Special Issue Selected Papers from "ECIS 2017")

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12 pages, 19136 KiB

Open AccessArticle

An Environmentally Friendly Approach for the Fabrication of Conductive Superhydrophobic Coatings with Sandwich-Like Structures

by Xiaomin Luo, Wenjie Hu, Min Cao, Huijun Ren, Jianyan Feng and Mengyuan Wei

Polymers 2018, 10(4), 378; https://doi.org/10.3390/polym10040378 - 30 Mar 2018

Cited by 9 | Viewed by 4840

Abstract

A large amount of research has been devoted to developing novel superhydrophobic coatings. However, it is still a great challenge to pursuean environmentally friendly method that leads to superhydrophobic coatings. Herein, we demonstrate for the first time, an environmentally friendly method for the [...] Read more.

A large amount of research has been devoted to developing novel superhydrophobic coatings. However, it is still a great challenge to pursuean environmentally friendly method that leads to superhydrophobic coatings. Herein, we demonstrate for the first time, an environmentally friendly method for the preparation of conductive superhydrophobic coatings with sandwich-like structures by using aminoethylaminopropyl polydimethylsiloxane modified waterborne polyurethane (SiWPU) and N-octadecylamine functionalized multi-wall carbon nanotubes. These environmentally friendly coatings with the sheet resistance of 1.1 ± 0.1 kΩ/sq exhibit a high apparent contact angle of 158.1° ± 2° and a low sliding angle below 1°. The influence of the surface texture before and after heat treatment on the wetting properties is discussed. In addition, the coatings can be electrically heated by 3~113 °C with a voltage of 12~72 V, and thus, can be used for deicing. Furthermore, the resulting coatings demonstrate good performance of wear resistance and ultraviolet resistance, which will have broad application potential in harsh environments. Full article

(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)

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15 pages, 15651 KiB

Open AccessArticle

The Length of Hydrophobic Chain in Amphiphilic Polypeptides Regulates the Efficiency of Gene Delivery

by Ying Zhang, Zhiping Zhou and Mingsheng Chen

Polymers 2018, 10(4), 379; https://doi.org/10.3390/polym10040379 - 1 Apr 2018

Cited by 19 | Viewed by 7687

Abstract

The major challenges of non-viral carriers are low transfection efficiency and high toxicity. To overcome this bottleneck, it is very important to investigate the structure-property-function (transfection efficiency) relationships of polycations. Herein, different length hydrophobic poly(l-leucine) chains in amphiphilic polypeptides were precisely [...] Read more.

The major challenges of non-viral carriers are low transfection efficiency and high toxicity. To overcome this bottleneck, it is very important to investigate the structure-property-function (transfection efficiency) relationships of polycations. Herein, different length hydrophobic poly(l-leucine) chains in amphiphilic polypeptides were precisely synthesized by α-amino acid N-carboxyanhydrides (NCA) ring-opening polymerization and these biocompatible polypeptides were chosen as a model to further examine the transfection in vitro. These polypeptides were characterized by nuclear magnetic resonance spectroscopy (NMR) and size exclusion chromatography (SEC). Agarose gel electrophoresis (AGE) was employed to validate the ability of DNA condensation and transmission electron microscopy (TEM) was used to observe the assemblies of polyplexes. Cytotoxicity was evaluated in COS-7 cell lines and transfection was performed in normal cell COS-7 and cancer cell Hep G2. The results showed that NCA monomers were prepared and the amphiphilic polypeptides, poly(lysine(CBZ))₅₀-block-poly(l-leucine)₁₀, poly(l-lysine(CBZ))₅₀-block-poly(l-leucine)₁₅, and poly(l-lysine(CBZ))₅₀-block-poly(l-leucine)₂₅, were successfully synthesized with controlled molecular weight and narrow distribution. After deprotection of CBZ, these materials can condense plasmid DNA into 100 nm nanoparticles and the cellular uptake of polyplexes was as fast as 30 min. The transfection data shown these materials had a good transfection efficiency comparing to polyethylenimine (Branched, 25 kDa) while they displayed ignored cytotoxicity. More importantly, we discovered the length of hydrophobic poly(l-leucine) in amphiphilic polypeptides steadily regulates gene delivery efficiency in two kinds of cells ranking poly(l-lysine)₅₀-block-poly(l-leucine)₂₅ > poly(l-lysine)₅₀-block-poly(l-leucine)₁₅ > poly(l-lysine)₅₀-block-poly(l-leucine)₁₀. Full article

(This article belongs to the Special Issue Polypeptide Containing Polymers)

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16 pages, 41131 KiB

Open AccessArticle

3D Porous Gelatin/PVA Hydrogel as Meniscus Substitute Using Alginate Micro-Particles as Porogens

by Alessandra Marrella, Alberto Lagazzo, Elena Dellacasa, Camilla Pasquini, Elisabetta Finocchio, Fabrizio Barberis, Laura Pastorino, Paolo Giannoni and Silvia Scaglione

Polymers 2018, 10(4), 380; https://doi.org/10.3390/polym10040380 - 1 Apr 2018

Cited by 40 | Viewed by 9098

Abstract

One of the current major challenges in orthopedic surgery is the treatment of meniscal lesions. Some of the main issues include mechanical consistency of meniscal implants, besides their fixation methods and integration with the host tissues. To tackle these aspects we realized a [...] Read more.

One of the current major challenges in orthopedic surgery is the treatment of meniscal lesions. Some of the main issues include mechanical consistency of meniscal implants, besides their fixation methods and integration with the host tissues. To tackle these aspects we realized a micro-porous, gelatin/polyvinyl alcohol (PVA)-based hydrogel to approach the high percentage of water present in the native meniscal tissue, recapitulating its biomechanical features, and, at the same time, realizing a porous implant, permissive to cell infiltration and tissue integration. In particular, we adopted aerodynamically-assisted jetting technology to realize sodium alginate micro-particles with controlled dimensions to be used as porogens. The porous hydrogels were realized through freezing-thawing cycles, followed by alginate particles leaching. Composite hydrogels showed a high porosity (74%) and an open porous structure, while preserving the elasticity behavior (E = 0.25 MPa) and high water content, typical of PVA-based hydrogels. The ex vivo animal model validation proved that the addition of gelatin, combined with the micro-porosity of the hydrogel, enhanced implant integration with the host tissue, allowing penetration of host cells within the construct boundaries. Altogether, these results show that the combined use of a water-insoluble micro-porogen and gelatin, as a bioactive agent, allowed the realization of a porous composite PVA-based hydrogel to be envisaged as a potential meniscal substitute. Full article

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26 pages, 38938 KiB

Open AccessArticle

Biocompatible Nanobioglass Reinforced Poly(ε-Caprolactone) Composites Synthesized via In Situ Ring Opening Polymerization

by Zoi Terzopoulou, Diana Baciu, Eleni Gounari, Theodore Steriotis, Georgia Charalambopoulou and Dimitrios Bikiaris

Polymers 2018, 10(4), 381; https://doi.org/10.3390/polym10040381 - 1 Apr 2018

Cited by 23 | Viewed by 4710

Abstract

Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester widely studied as a biomaterial for tissue engineering and controlled release applications, but its low bioactivity and weak mechanical performance limits its applications. In this work, nanosized bioglasses with two different compositions (SiO₂–CaO and [...] Read more.

Poly(ε-caprolactone) (PCL) is a bioresorbable synthetic polyester widely studied as a biomaterial for tissue engineering and controlled release applications, but its low bioactivity and weak mechanical performance limits its applications. In this work, nanosized bioglasses with two different compositions (SiO₂–CaO and SiO₂–CaO–P₂O₅) were synthesized with a hydrothermal method, and each one was used as filler in the preparation of PCL nanocomposites via the in situ ring opening polymerization of ε-caprolactone. The effect of the addition of 0.5, 1 and 2.5 wt % of the nanofillers on the molecular weight, structural, mechanical and thermal properties of the polymer nanocomposites, as well as on their enzymatic hydrolysis rate, bioactivity and biocompatibility was systematically investigated. All nanocomposites exhibited higher molecular weight values in comparison with neat PCL, and mechanical properties were enhanced for the 0.5 and 1 wt % filler content, which was attributed to extensive interactions between the filler and the matrix, proving the superiority of in situ polymerization over solution mixing and melt compounding. Both bioglasses accelerated the enzymatic degradation of PCL and induced bioactivity, since apatite was formed on the surface of the nanocomposites after soaking in simulated body fluid. Finally, all samples were biocompatible as Wharton jelly-derived mesenchymal stem cells (WJ-MSCs) attached and proliferated on their surfaces. Full article

(This article belongs to the Special Issue New Developments in Ring-Opening Polymerization)

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13 pages, 1692 KiB

Open AccessArticle

The Effect of Maleated Polypropylene on the Non-Isothermal Crystallization Kinetics of Wood Fiber-Reinforced Polypropylene Composites

by Chung-Wei Huang, Teng-Chun Yang, Ke-Chang Hung, Jin-Wei Xu and Jyh-Horng Wu

Polymers 2018, 10(4), 382; https://doi.org/10.3390/polym10040382 - 1 Apr 2018

Cited by 26 | Viewed by 5598

Abstract

The influence of maleated polypropylene (MAPP) on the non-isothermal crystallization behavior of wood fiber (WF)-reinforced PP composites (WPCs) was investigated by a differential scanning calorimeter (DSC). The results showed that MAPP as a nucleation agent accelerated the crystallization rate of the PP matrix [...] Read more.

The influence of maleated polypropylene (MAPP) on the non-isothermal crystallization behavior of wood fiber (WF)-reinforced PP composites (WPCs) was investigated by a differential scanning calorimeter (DSC). The results showed that MAPP as a nucleation agent accelerated the crystallization rate of the PP matrix in WPC under the cooling process. The corresponding crystallization kinetics and activation energy were further analyzed using the Avrami method, Avrami–Ozawa method, Kissinger method, and Friedman method. The results demonstrated that MAPP significantly changed the crystal growth mechanism of the PP matrix to heterogeneous nucleation for acicular and tabular crystal growth during the annealing step. A remarkably lower cooling rate can achieve a certain relative crystallinity degree at the unit crystallization time for WPC with 3 wt % MAPP (WPC_M3). Similarly, the lowest crystallization activation energy was observed for the WPC_M3 among all WPCs by the Kissinger method. Furthermore, based on the Friedman method, the addition of MAPP easily caused the PP matrix to crystallize in the WPC at the initial stage of relative crystallinity. Full article

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15 pages, 14105 KiB

Open AccessArticle

Investigation on the Nanomechanics of Liposome Adsorption on Titanium Alloys: Temperature and Loading Effects

by Yiqin Duan, Yuhong Liu, Jinjin Li, Hongdong Wang and Shizhu Wen

Polymers 2018, 10(4), 383; https://doi.org/10.3390/polym10040383 - 1 Apr 2018

Cited by 15 | Viewed by 4455

Abstract

The mechanical properties of liposomes, determined by the lipid phase state at ambient temperature, have a close relationship with their physiological activities. Here, atomic force microscopy (AFM) was used to produce images and perform force measurements on titanium alloys at two adsorbed temperatures. [...] Read more.

The mechanical properties of liposomes, determined by the lipid phase state at ambient temperature, have a close relationship with their physiological activities. Here, atomic force microscopy (AFM) was used to produce images and perform force measurements on titanium alloys at two adsorbed temperatures. The mechanical properties were evaluated under repeated loading and unloading, suggesting a better reversibility and resistance of gel phase liposomes. The liquid phase liposomes were irreversibly damaged during the first approach while the gel phase liposomes could bear more iterations, resulting from water flow reversibly going across the membranes. The statistical data offered strong evidence that the lipid membranes in the gel phase are robust enough to resist the tip penetration, mainly due to their orderly organization and strong hydrophobic interactions between lipid molecules. This work regarding the mechanical properties of liposomes with different phases provides guidance for future clinical applications, such as artificial joints. Full article

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15 pages, 18344 KiB

Open AccessArticle

Structure-Function Relationships in PMA and PMAT Series Copolymers for Polymer Solar Cells

by Jhe-Han Chen, Chi-Kan Liu, Wei-Che Chang, Pai-Tao Sah and Li-Hsin Chan

Polymers 2018, 10(4), 384; https://doi.org/10.3390/polym10040384 - 1 Apr 2018

Viewed by 4657

Abstract

Two series (PMA and PMAT) of two-dimensional donor-acceptor copolymers consisting of a 3,4-bis(4-bromophenyl)maleimide derivative and triphenylamine with a conjugated side chain were designed and synthesized to probe their structure-function relationships for use in bulk heterojunction (BHJ) polymer solar cells (PSCs). The difference between [...] Read more.

Two series (PMA and PMAT) of two-dimensional donor-acceptor copolymers consisting of a 3,4-bis(4-bromophenyl)maleimide derivative and triphenylamine with a conjugated side chain were designed and synthesized to probe their structure-function relationships for use in bulk heterojunction (BHJ) polymer solar cells (PSCs). The difference between PMA- and PMAT-series is the conjugated side chain length on the triphenylamine unit. By extending the side chain length, and by attaching various acceptor end groups to the side chain, the electronic and photophysical properties of these copolymers, as well as subsequent device performance, were significantly affected. Two series of copolymers showed broad absorption in the visible region with two obvious peaks. With increasing electron-withdrawing strength of the acceptor end groups, the intramolecular charge transfer peak becomes progressively red-shifted. Highest occupied molecular orbital (HOMO) levels in each copolymer series are similar, but lowest unoccupied molecular orbital (LUMO) levels are dictated by the acceptors. BHJ PSCs composed of the copolymers as a donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC₇₁BM) as an acceptor in 1:2 weight ratio were fabricated and characterized. PSCs based on PMA- and PMAT-series copolymers had power conversion efficiencies (PCEs) ranging from 2.05–2.16% and 3.14–4.01%, respectively. These results indicate that subtle tuning of the chemical structure can significantly influence PSC device performance. Full article

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9 pages, 1119 KiB

Open AccessArticle

Recyclable Heterogeneous Chitosan Supported Copper Catalyst for Silyl Conjugate Addition to α,β-Unsaturated Acceptors in Water

by Lei Zhu, Bojie Li, Shan Wang, Wei Wang, Liansheng Wang, Liang Ding and Caiqin Qin

Polymers 2018, 10(4), 385; https://doi.org/10.3390/polym10040385 - 1 Apr 2018

Cited by 14 | Viewed by 3993

Abstract

The first example of an environmentally-benign chitosan supported copper catalyzed conjugate silylation of α,β-unsaturated acceptors was accomplished in water under mild conditions. This protocol provides an efficient pathway to achieve an important class of β-silyl carbonyl compounds and the desired products were obtained [...] Read more.

The first example of an environmentally-benign chitosan supported copper catalyzed conjugate silylation of α,β-unsaturated acceptors was accomplished in water under mild conditions. This protocol provides an efficient pathway to achieve an important class of β-silyl carbonyl compounds and the desired products were obtained in good to excellent yields. Gram-scale synthesis and easy transformation of obtained β-silyl products were also been demonstrated. Remarkably, this chitosan supported copper catalyst can be easily recycled and reused six times without any significant decrease of catalytic activity. The advantages of this newly developed method include operational simplicity, good functional group tolerance, scale-up ability, ready availability, and easy recyclability of catalyst. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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22 pages, 30159 KiB

Open AccessArticle

New Poly(lactic acid) Active Packaging Composite Films Incorporated with Fungal Melanin

by Łukasz Łopusiewicz, Filip Jędra and Małgorzata Mizielińska

Polymers 2018, 10(4), 386; https://doi.org/10.3390/polym10040386 - 1 Apr 2018

Cited by 76 | Viewed by 10233

Abstract

In this work, fungal melanin was used for the first time to prepare poly(lactic acid)-based composites. The films of various melanin concentrations (0.025%, 0.05% and 0.2% w/w) were prepared using an extrusion method. The mechanical, antioxidant, antimicrobial, water vapor and [...] Read more.

In this work, fungal melanin was used for the first time to prepare poly(lactic acid)-based composites. The films of various melanin concentrations (0.025%, 0.05% and 0.2% w/w) were prepared using an extrusion method. The mechanical, antioxidant, antimicrobial, water vapor and UV-Vis barrier properties, as well as available polyphenolics on the surface, were studied. FT-IR and Raman spectroscopy studies were carried out to analyze the chemical composition of the resulting films. The hydrophobicity, color response, thermal, optical properties, and opacity values were also determined. The results of this study show that the addition of fungal melanin to poly(lactic acid) (PLA) as a modifier influenced mechanical and water vapor barrier properties depending on melanin concentration. In low concentration, melanin enhanced the mechanical and barrier properties of the modified films, but in larger amounts, the properties were decreased. The UV-Vis barrier properties of PLA/melanin composites were marginally improved. Differential Scanning Calorimetry (DSC) analysis indicated that crystallinity of PLA increased by the addition of melanin, but this did not affect the thermal stability of the films. Modified PLA/melanin films showed good antioxidant activity and were active against Enterococcus faecalis, Pseudomonas aeruginosa and Pseudomonas putida. The addition of melanin caused changes in color values, decreasing lightness and increasing the redness and yellowness of films. Based on the results of this study, fungal melanin has good potential to be exploited as a value-added modifier that can improve the overall properties of PLA. Full article

(This article belongs to the Special Issue Polymers for Packaging Applications)

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20 pages, 2377 KiB

Open AccessArticle

Exploring the Molecular Distributions in Dilute Polymer Solutions Using a Multi-Scale Numerical Solver

by Yi Liu, Canqun Yang, Cheng-Kun Wu, Xiang Zhang, Xin Zhang and Xiao-Wei Guo

Polymers 2018, 10(4), 387; https://doi.org/10.3390/polym10040387 - 1 Apr 2018

Cited by 3 | Viewed by 3244

Abstract

Simulating the rheological behaviors of polymer solutions is intrinsically a multi-scale problem. To study the macroscopic and microscopic characteristics in the fluid flow of dilute polymer solutions, we designed a multi-scale solver, which couples the Brownian Configuration Fields with the macroscopic hydrodynamic governing [...] Read more.

Simulating the rheological behaviors of polymer solutions is intrinsically a multi-scale problem. To study the macroscopic and microscopic characteristics in the fluid flow of dilute polymer solutions, we designed a multi-scale solver, which couples the Brownian Configuration Fields with the macroscopic hydrodynamic governing equations. Numerical simulation results using the multi-scale solver exhibited good accordance with the macroscopic only approach. Through a scalar field D we also quantitatively studied the flow behaviours in 2D planar channels, and analyzed the correlation between the molecular distribution and the macroscopic fluid flow in polymer solutions. Our results verified the correctness of the solver, which could provide valuable guidance for multi-scale simulations of complex fluids based on OpenFOAM. Full article

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12 pages, 24838 KiB

Open AccessArticle

Improving the Mechanical and Electrical Properties of Ceramizable Silicone Rubber/Halloysite Composites and Their Ceramic Residues by Incorporation of Different Borates

by Jianhua Guo, Xuming Chen and Yong Zhang

Polymers 2018, 10(4), 388; https://doi.org/10.3390/polym10040388 - 1 Apr 2018

Cited by 30 | Viewed by 5487

Abstract

Ceramizable silicone rubber (MVQ)/halloysite (HNT) composites were fabricated by incorporation of three different borates, including sodium tetraborate decahydrate, ammonium pentaborate, and zinc borate into MVQ matrix, respectively. The composites without any borates were also prepared as control. The effect of the borates on [...] Read more.

Ceramizable silicone rubber (MVQ)/halloysite (HNT) composites were fabricated by incorporation of three different borates, including sodium tetraborate decahydrate, ammonium pentaborate, and zinc borate into MVQ matrix, respectively. The composites without any borates were also prepared as control. The effect of the borates on the mechanical and electrical properties of MVQ/HNT composites was investigated. The ceramic residues were obtained from the decomposition of the composites after sintering at 1000 °C. The effect of the borates on the linear shrinkage, weight loss, and flexural and impact strength of the residues was also studied. The fracture surfaces of the composites and their corresponding residues were observed by SEM. The proposed ceramizable mechanism of the composites by incorporation of different borates was revealed by XRD analysis. Full article

(This article belongs to the Special Issue Siloxane-Based Polymers)

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11 pages, 12618 KiB

Open AccessArticle

Hypoxia-Responsive Mesoporous Nanoparticles for Doxorubicin Delivery

by Shakera Khatoon, Hwa Seung Han, Jueun Jeon, N. Vijayakameswara Rao, Dae-Woong Jeong, M. Ikram, T. Yasin, Gi-Ra Yi and Jae Hyung Park

Polymers 2018, 10(4), 390; https://doi.org/10.3390/polym10040390 - 1 Apr 2018

Cited by 25 | Viewed by 6272

Abstract

Hypoxia, or low oxygen tension, is a common feature of solid tumors. Here, we report hypoxia-responsive mesoporous silica nanoparticles (HR-MSNs) with a 4-nitroimidazole-β-cyclodextrin (NI-CD) complex that is acting as the hypoxia-responsive gatekeeper. When these CD-HR-MSNs encountered a hypoxic environment, the nitroimidazole (NI) gatekeeper [...] Read more.

Hypoxia, or low oxygen tension, is a common feature of solid tumors. Here, we report hypoxia-responsive mesoporous silica nanoparticles (HR-MSNs) with a 4-nitroimidazole-β-cyclodextrin (NI-CD) complex that is acting as the hypoxia-responsive gatekeeper. When these CD-HR-MSNs encountered a hypoxic environment, the nitroimidazole (NI) gatekeeper portion of CD-HR-MSNs disintegrated through bioreduction of the hydrophobic NI state to the hydrophilic NI state. Under hypoxic conditions, the release rate of doxorubicin (DOX) from DOX-loaded CD-HR-MSNs (DOX-CD-HR-MSNs) increased along with the disintegration of the gatekeeper. Conversely, DOX release was retarded under normoxic conditions. In vitro experiments confirmed that DOX-CD-HR-MSNs exhibit higher toxicity to hypoxic cells when compared to normoxic cells. Confocal microscopy images indicated that DOX-CD-HR-MSNs effectively release DOX into SCC-7 cells under hypoxic conditions. These results demonstrate that CD-HR-MSNs can release drugs in a hypoxia-responsive manner, and thus are promising drug carriers for hypoxia-targeted cancer therapy. Full article

(This article belongs to the Special Issue Polymeric Micro/Nanoparticles for Bio-Medical Applications)

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22 pages, 15543 KiB

Open AccessArticle

Single-Point Incremental Forming of Two Biocompatible Polymers: An Insight into Their Thermal and Structural Properties

by Luis Marcelo Lozano-Sánchez, Isabel Bagudanch, Alan Osiris Sustaita, Jackeline Iturbe-Ek, Luis Ernesto Elizalde, Maria Luisa Garcia-Romeu and Alex Elías-Zúñiga

Polymers 2018, 10(4), 391; https://doi.org/10.3390/polym10040391 - 1 Apr 2018

Cited by 45 | Viewed by 5302

Abstract

Sheets of polycaprolactone (PCL) and ultra-high molecular weight polyethylene (UHMWPE) were fabricated and shaped by the Single-Point Incremental Forming process (SPIF). The performance of these biocompatible polymers in SPIF was assessed through the variation of four main parameters: the diameter of the forming [...] Read more.

Sheets of polycaprolactone (PCL) and ultra-high molecular weight polyethylene (UHMWPE) were fabricated and shaped by the Single-Point Incremental Forming process (SPIF). The performance of these biocompatible polymers in SPIF was assessed through the variation of four main parameters: the diameter of the forming tool, the spindle speed, the feed rate, and the step size based on a Box–Behnken design of experiments of four variables and three levels. The design of experiments allowed us to identify the parameters that most affect the forming of PCL and UHMWPE. The study was completed by means of a deep characterization of the thermal and structural properties of both polymers. These properties were correlated to the performance of the polymers observed in SPIF, and it was found that the polymer chains are oriented as a consequence of the SPIF processing. Moreover, by X-ray diffraction it was proved that polymer chains behave differently on each surface of the fabricated parts, since the chains on the surface in contact with the forming tool are oriented horizontally, while on the opposite surface they are oriented in the vertical direction. The unit cell of UHMWPE is distorted, passing from an orthorhombic cell to a monoclinic due to the slippage between crystallites. This slippage between crystallites was observed in both PCL and UHMWPE, and was identified as an alpha star thermal transition located in the rubbery region between the glass transition and the melting point of each polymer. Full article

(This article belongs to the Special Issue Processing-Structure-Properties Relationships in Polymers)

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17 pages, 3371 KiB

Open AccessArticle

Reversible pH-Sensitive Chitosan-Based Hydrogels. Influence of Dispersion Composition on Rheological Properties and Sustained Drug Delivery

by Nieves Iglesias, Elsa Galbis, Concepción Valencia, M.-Violante De-Paz and Juan A. Galbis

Polymers 2018, 10(4), 392; https://doi.org/10.3390/polym10040392 - 1 Apr 2018

Cited by 25 | Viewed by 6626

Abstract

The present work deals with the synthesis of micro-structured biomaterials based on chitosan (CTS) for their applications as biocompatible carriers of drugs and bioactive compounds. Twelve dispersions were prepared by means of functional cross-linking with tricarballylic acid (TCA); they were characterized by Fourier [...] Read more.

The present work deals with the synthesis of micro-structured biomaterials based on chitosan (CTS) for their applications as biocompatible carriers of drugs and bioactive compounds. Twelve dispersions were prepared by means of functional cross-linking with tricarballylic acid (TCA); they were characterized by Fourier transform infrared spectroscopy (FT-IR), modulated temperature differential scanning calorimetry (MTDSC) and scanning electron microscopy (SEM), and their rheological properties were studied. To the best of the authors’ knowledge, no study has been carried out on the influence of CTS concentration, degree of cross-linking and drug loading on chitosan hydrogels for drug delivery systems (DDS) and is investigated herein for the first time. The influence of dispersion composition (polymer concentration and degree of cross-linking) revealed to exert a marked impact on its rheological properties, going from liquid-like to viscoelastic gels. The release profiles of a model drug, diclofenac sodium (DCNa), as well as their relationships with polymer concentration, drug loading and degree of cross-linking were evaluated. Similar to the findings on rheological properties, a wide range of release profiles was encountered. These formulations were found to display a well-controlled drug release strongly dependent on the formulation composition. Cumulative drug release under physiological conditions for 96 h ranged from 8% to 67%. For comparative purpose, Voltaren emulgel^® from Novartis Pharmaceuticals was also investigated and the latter was the formulation with the highest cumulative drug release (85%). Some formulations showed similar spreadability values to the commercial hydrogel. The comparative study of three batches confirmed the reproducibility of the method, leading to systems particularly suitable for their use as drug carriers. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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11 pages, 14728 KiB

Open AccessArticle

Preparation of Maleic Anhydride Grafted Polybutene and Its Application in Isotactic Polybutene-1/Microcrystalline Cellulose Composites

by Bo Wang, Kai Nie, Xiao-rong Xue, Fu-hua Lin, Xiang-yang Li, Yong-bing Xue and Jun Luo

Polymers 2018, 10(4), 393; https://doi.org/10.3390/polym10040393 - 2 Apr 2018

Cited by 23 | Viewed by 4295

Abstract

Microcrystalline cellulose (MCC) offers great potential to improve the mechanical and crystallization properties of isotactic polybutene-1 (iPB) because of its low cost, biodegradability, renewability and excellent mechanical properties. However, the compatibility of polar MCC and non-polar iPB is poor. In this study, maleic [...] Read more.

Microcrystalline cellulose (MCC) offers great potential to improve the mechanical and crystallization properties of isotactic polybutene-1 (iPB) because of its low cost, biodegradability, renewability and excellent mechanical properties. However, the compatibility of polar MCC and non-polar iPB is poor. In this study, maleic anhydride grafted polybutene (MAPB) was prepared by the solution method and was used as a compatibilizer in the fabrication of iPB/MCC composites by using a twin screw extruder. The ultimate tensile strength, tensile modulus, flexural strength, flexural modulus of the iPB/MCC composites increased by 3.1%, 16.5%, 10.7%, 6.5%, respectively, compared with that of pure iPB. With MAPB addition, these values increased by 17.2%, 31%, 17.5% and 10%, respectively, compared with that of pure iPB. The heat-distortion temperature and thermal-decomposition temperature of all composites increased with an increased MCC content. The non-isothermal crystallization of the iPB/MCC composites shows that MCC addition can promote iPB crystallization, because the non-isothermal crystallization curve of the composites moves toward a higher temperature, especially after MAPB addition. Scanning electron micrographs indicate that the compatibility of the iPB/MCC has been enhanced significantly. Full article

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13 pages, 24135 KiB

Open AccessArticle

DNA Phase Transition in Charge Neutralization and Comformation Induced by Trivalent-Hydrolysed Metal Ions

by Zhaoxu Luo, Yanwei Wang, Shuhang Li and Guangcan Yang

Polymers 2018, 10(4), 394; https://doi.org/10.3390/polym10040394 - 2 Apr 2018

Cited by 4 | Viewed by 4746

Abstract

It is well known that common trivalent counter ions can induce DNA compaction or condensation but are unable to invert DNA surface charge in a normal aqueous solution. In the present study, we found that trivalent-hydrolysed metal ions (Fe³⁺, Al³⁺ [...] Read more.

It is well known that common trivalent counter ions can induce DNA compaction or condensation but are unable to invert DNA surface charge in a normal aqueous solution. In the present study, we found that trivalent-hydrolysed metal ions (Fe³⁺, Al³⁺) are not only capable of inducing DNA condensation, but they also invert the electrophoretic mobility of DNA by electrophoretic light scattering and single molecular techniques. In comparison with neutral trivalent cations, hydrolysed metal ions such as Fe³⁺ can induce DNA condensation at a much lower concentration of cations, and its corresponding morphology of condensed DNA was directly observed by atomic force microscopy (AFM). The condensing and unravelling forces of DNA condensates were measured by tethering DNA by magnetic tweezers (MT) measurements at various concentration of Fe³⁺ and Al³⁺. We found that a coil–globule transition of DNA by hydrolysed metal ions not only was observed in DNA-complex sizes, but also in the curve of electrophoretic mobility of DNA in solution. In contrast, the transition was not observed in the case of neutral trivalent cations such as La³⁺ and Co³⁺. We attribute the transition and charge inversion to the ion-specific interaction between hydrolysed metal ions and phosphates of DNA backbone. Full article

(This article belongs to the Special Issue Ionic Polymers)

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13 pages, 2445 KiB

Open AccessArticle

Antioxidant Activity and Antifungal Activity of Chitosan Derivatives with Propane Sulfonate Groups

by Fang Luan, Lijie Wei, Jingjing Zhang, Yingqi Mi, Fang Dong, Qing Li and Zhanyong Guo

Polymers 2018, 10(4), 395; https://doi.org/10.3390/polym10040395 - 3 Apr 2018

Cited by 32 | Viewed by 4909

Abstract

We successfully synthesized the water-soluble chitosan derivatives propane sulfonated chitosan (PSCS) and dipropane sulfonated chitosan (DPSCS) in this paper. These derivatives were characterized by FTIR, ¹H NMR, and ¹³C NMR. Moreover, the antioxidant activity of the chitosan derivatives was evaluated by [...] Read more.

We successfully synthesized the water-soluble chitosan derivatives propane sulfonated chitosan (PSCS) and dipropane sulfonated chitosan (DPSCS) in this paper. These derivatives were characterized by FTIR, ¹H NMR, and ¹³C NMR. Moreover, the antioxidant activity of the chitosan derivatives was evaluated by free radical scavenging ability (against DPPH-radical, hydroxyl-radical, and superoxide-radical) and ferric reducing power. Meanwhile, inhibitory effects against two fungi were also tested. Our results suggested antioxidant abilities and antifungal properties were in order of DPSCS > PSCS > CS, which were consistent with the number of propane sulfonated groups. The scavenging activity of DPSCS against superoxide-radical and DPPH-radical were 94.1% and 100% at 1.6 mg/mL, respectively. The inhibitory indices of DPSCS against P. asparagi and F. oxysporum were up to 82.2% and 94% at 1.0 mg/mL, respectively. Obviously, the number of propane sulfonated groups of chitosan derivatives not only contributes to antioxidant activity, but also to antifungal activity. Therefore, DPSCS with more propane sulfonated groups endowed with antioxidant and antifungal activity that can be used as a candidate material in the food and pharmaceutical industries. Full article

(This article belongs to the Collection Polysaccharides)

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10 pages, 6985 KiB

Open AccessArticle

Incorporation of Coumarin-Based Fluorescent Monomers into Co-Oligomeric Molecules

by Edgar Teixeira, João C. Lima, A. Jorge Parola and Paula S. Branco

Polymers 2018, 10(4), 396; https://doi.org/10.3390/polym10040396 - 3 Apr 2018

Cited by 5 | Viewed by 4653

Abstract

With the purpose of modifying organic fluorescent dyes based on the coumarin scaffold, and developing and evaluating a route to its incorporation into a polymeric backbone, a study was conducted on the co-polymerization of 3-vinylcoumarins with styrene and methyl acrylate using 2,2-azobis(isobutyronitrile) (AIBN) [...] Read more.

With the purpose of modifying organic fluorescent dyes based on the coumarin scaffold, and developing and evaluating a route to its incorporation into a polymeric backbone, a study was conducted on the co-polymerization of 3-vinylcoumarins with styrene and methyl acrylate using 2,2-azobis(isobutyronitrile) (AIBN) as the radical initiator. The structural and photophysical characterization proved the incorporation of the coumarin monomers into the polymeric chain and further showed a decrease in the fluorescence quantum yields in the co-oligomers. Full article

(This article belongs to the Special Issue Polymeric Materials for Optical Applications)

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17 pages, 9926 KiB

Open AccessArticle

Effect of Ionizing Radiation on the Chemical Structure and the Physical Properties of Polycaprolactones of Different Molecular Weight

by Rodrigo Navarro, Guillermina Burillo, Esbaide Adem and Angel Marcos-Fernández

Polymers 2018, 10(4), 397; https://doi.org/10.3390/polym10040397 - 3 Apr 2018

Cited by 29 | Viewed by 7693

Abstract

Polymers used in the biomedical sector can be exposed to ionizing radiation (X-ray, gamma) in vivo as implants or ex vivo for sterilization purposes (gamma, electron beam). This ionizing radiation can, at certain levels, cause degradation of the polymer. Polycaprolactones (PCL) of different [...] Read more.

Polymers used in the biomedical sector can be exposed to ionizing radiation (X-ray, gamma) in vivo as implants or ex vivo for sterilization purposes (gamma, electron beam). This ionizing radiation can, at certain levels, cause degradation of the polymer. Polycaprolactones (PCL) of different molecular weights were irradiated with electron beam and the changes in their chemical structure and physical properties with the dose were evaluated. Electron beam irradiation produced crosslinking and chain scission in the PCL chain without significant predominance of one mechanism over the other. Minimum dose for gelation decreased with the increase in PCL molecular weight whereas crosslinking efficiency was almost independent of PCL molecular weight. Carboxylic groups, hydroxyl groups and new saturated hydrocarbon species were detected by proton nuclear magnetic resonance (NMR). These species were consistent with a mechanism where chain scission could take place at any bond in the PCL chain with preference in the –COO–CH₂– bond. Crosslinking decreased significantly the crystallization temperature of PCL. Tensile properties decreased continuously with the increase in dose. Irradiation with gamma rays produced a faster decay in mechanical properties than electron beam. Full article

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14 pages, 10233 KiB

Open AccessFeature PaperArticle

A Facile, One-Pot, Surfactant-Free Nanoprecipitation Method for the Preparation of Nanogels from Polyglycerol–Drug Conjugates that Can Be Freely Assembled for Combination Therapy Applications

by Laura I. Vossen, Stefanie Wedepohl and Marcelo Calderón

Polymers 2018, 10(4), 398; https://doi.org/10.3390/polym10040398 - 3 Apr 2018

Cited by 14 | Viewed by 6839

Abstract

A well-established strategy to treat drug resistance is the use of multiple therapeutics. Polymer-based drug delivery systems (DDS) can facilitate a simultaneous delivery of two or more drugs. In this study, we developed and synthesized a dendritic polyglycerol (PG) nanogel (NG) system that [...] Read more.

A well-established strategy to treat drug resistance is the use of multiple therapeutics. Polymer-based drug delivery systems (DDS) can facilitate a simultaneous delivery of two or more drugs. In this study, we developed and synthesized a dendritic polyglycerol (PG) nanogel (NG) system that allows for free combination of different fixed ratios of active compound conjugates within a single NG particle. As a proof of concept, we synthesized NGs bearing the chemotherapeutic agent doxorubicin (DOX) and paclitaxel (PTX) in different ratios, as well as conjugated dye molecules. Our combination PG NGs were formed by simply mixing PG–drug/dye conjugates bearing free thiol groups with PG-acrylate in an inverse surfactant-free nanoprecipitation method. With this method we obtained PG-NGs in the size range of 110–165 nm with low polydispersity indices. Solubility of hydrophobic PTX was improved without the need for additional solubilizing agents such as polyethylene glycol (PEG). Interestingly, we found that our NGs made from PG-DOX conjugates have a high quenching efficiency for DOX, which could be interesting for theranostic purposes. Full article

(This article belongs to the Special Issue Polymers for Therapy and Diagnostics)

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10 pages, 5073 KiB

Open AccessArticle

Synthesis of a Flexible Freestanding Sulfur/Polyacrylonitrile/Graphene Oxide as the Cathode for Lithium/Sulfur Batteries

by Huifen Peng, Xiaoran Wang, Yan Zhao, Taizhe Tan, Zhumabay Bakenov and Yongguang Zhang

Polymers 2018, 10(4), 399; https://doi.org/10.3390/polym10040399 - 3 Apr 2018

Cited by 19 | Viewed by 4932

Abstract

Rechargeable lithium/sulfur (Li/S) batteries have received quite significant attention over the years because of their high theoretical specific capacity (1672 mAh·g⁻¹) and energy density (2600 mAh·g⁻¹) which has led to more efforts for improvement in their electrochemical performance. Herein, [...] Read more.

Rechargeable lithium/sulfur (Li/S) batteries have received quite significant attention over the years because of their high theoretical specific capacity (1672 mAh·g⁻¹) and energy density (2600 mAh·g⁻¹) which has led to more efforts for improvement in their electrochemical performance. Herein, the synthesis of a flexible freestanding sulfur/polyacrylonitrile/graphene oxide (S/PAN/GO) as the cathode for Li/S batteries by simple method via vacuum filtration is reported. The S/PAN/GO hybrid binder-free electrode is considered as one of the most promising cathodes for Li/S batteries. Graphene oxide (GO) slice structure provides effective ion conductivity channels and increases structural stability of the ternary system, resulting in excellent electrochemical properties of the freestanding S/PAN/GO cathode. Additionally, graphene oxide (GO) membrane was able to minimize the polysulfides’ dissolution and their shuttle, which was attributed to the electrostatic interactions between the negatively-charged species and the oxygen functional groups on GO. Furthermore, these oxygen-containing functional groups including carboxyl, epoxide and hydroxyl groups provide active sites for coordination with inorganic materials (such as sulfur). It exhibits the initial reversible specific capacity of 1379 mAh·g⁻¹ at a constant current rate of 0.2 C and maintains 1205 mAh·g⁻¹ over 100 cycles (~87% retention). In addition, the freestanding S/PAN/GO cathode displays excellent coulombic efficiency (~100%) and rate capability, delivering up to 685 mAh·g⁻¹ capacity at 2 C. Full article

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18 pages, 43481 KiB

Open AccessArticle

Microstructure Development and Its Influence on the Properties of Styrene-Ethylene-Butylene-Styrene/Polystyrene Blends

by Ritima Banerjee, Suprakas Sinha Ray and Anup K. Ghosh

Polymers 2018, 10(4), 400; https://doi.org/10.3390/polym10040400 - 4 Apr 2018

Cited by 20 | Viewed by 5626

Abstract

The present work is a novel attempt to understand the microstructure of styrene-ethylene-butylene-styrene (SEBS)/polystyrene (PS) blends not only through morphological studies, but also thermal, mechanical and rheological characterizations. SEBS/PS blends containing 10, 30 and 50 wt % PS were processed in a micro-compounder [...] Read more.

The present work is a novel attempt to understand the microstructure of styrene-ethylene-butylene-styrene (SEBS)/polystyrene (PS) blends not only through morphological studies, but also thermal, mechanical and rheological characterizations. SEBS/PS blends containing 10, 30 and 50 wt % PS were processed in a micro-compounder and characterized. Scanning electron microscopy (SEM) studies, with selective staining of the PS phase, revealed the presence of PS as nanometer-sized domains, as well as phase-separated micrometer-sized aggregates. Blends with 30 and 50 wt % PS exhibited a fibrillar microstructure, obeying Hirsch’s model of short fiber composites. A remarkable increase in glass transition temperature indicated a strong interaction of the fibrils with SEBS. All blends showed two modes of relaxation corresponding to the two phases. A single mode of relaxation of the PS phase has been attributed to combined effects of the partial miscibility of the added PS, along with the interaction of the fibrils with SEBS. The long relaxation time of the elastomeric phase indicated the tendency of these materials to undergo time-dependent shrinkage in secondary processing operations. An increase in PS content resulted in the lowering of the shear viscosity and energy requirement for mixing, indicating the ease of processing. Full article

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14 pages, 17050 KiB

Open AccessArticle

Thermo-Mechanical Performance of Polylactide Composites Reinforced with Alkali-Treated Bamboo Fibers

by Fang Wang, Shujue Zhou, Mengqing Yang, Zhiqian Chen and Siyan Ran

Polymers 2018, 10(4), 401; https://doi.org/10.3390/polym10040401 - 4 Apr 2018

Cited by 56 | Viewed by 4695

Abstract

In this study, polylactide acid (PLA) is filled with bamboo fibers (BFs) to fabricate a biodegradable natural composite for industrial applications. The influence of pre-treatment of BFs using 4 wt % sodium hydroxide (NaOH) solution at room temperature for 1 h on thermal [...] Read more.

In this study, polylactide acid (PLA) is filled with bamboo fibers (BFs) to fabricate a biodegradable natural composite for industrial applications. The influence of pre-treatment of BFs using 4 wt % sodium hydroxide (NaOH) solution at room temperature for 1 h on thermal and mechanical properties of resultant composites is systematically investigated. Differential scanning calorimetry and thermogravimetric analysis demonstrate that the incorporation of treated BFs promotes higher glass transition and crystallization temperatures of the resultant composites relative to untreated fiber composites, whereas alkali treatment results in superior thermal stability. Furthermore, the fracture surfaces are characterized by scanning electron microscopy. The changes in morphology reveal the possible dissolution of hemicellulose and lignin by alkalization with NaOH, indicative of an improved interfacial adhesion. An increment in the tensile strength of composites is achieved through the reinforcement with treated fibers. However, a lower tensile modulus is found for composites reinforced with chemically modified BFs, which might be due to the partial conversion of cellulose I into II. The results highlight that the use of BFs could be a feasible candidate as reinforcements for the development of biodegradable composites. Full article

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21 pages, 33374 KiB

Open AccessArticle

Isocyanate-Free Polyurethane Coatings and Adhesives from Mono- and Di-Saccharides

by Xuedong Xi, Antonio Pizzi and Luc Delmotte

Polymers 2018, 10(4), 402; https://doi.org/10.3390/polym10040402 - 4 Apr 2018

Cited by 66 | Viewed by 9197

Abstract

Mostly biosourced non-isocyanate polyurethanes (NIPU) were prepared from mono- and disaccharides, namely glucose and sucrose, reacted with dimethyl carbonate and hexamethylene diamine. The main aim of this research was to show that NIPU can be prepared from mono- and disaccharides, this just being [...] Read more.

Mostly biosourced non-isocyanate polyurethanes (NIPU) were prepared from mono- and disaccharides, namely glucose and sucrose, reacted with dimethyl carbonate and hexamethylene diamine. The main aim of this research was to show that NIPU can be prepared from mono- and disaccharides, this just being an initial exploratory work and its sole main aim. The oligomers obtained were detected by MALDI-ToF, CP-MAS ¹³C NMR, and FTIR spectrometries. The glucose-derived NIPU were shown to harden at a markedly lower temperature than the sucrose-derived ones and to be easier to handle and spread. The NIPU obtained were applied as wood and steel surface coatings and tested by the sessile drop test (on wood) and cross-cut test (on steel) with encouraging results. The glucose NIPU gave good surface coating results already at 103 °C, while the sucrose NIPU yielded good results only at a markedly higher temperature of hardening. The NIPU saccharide resins were also tested as thermosetting wood joint adhesives with the glucose NIPU yielding very encouraging results. Full article

(This article belongs to the Collection Polymeric Adhesives)

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12 pages, 10665 KiB

Open AccessArticle

The Effect of Alkali Treatment on Properties of Dopamine Modification of Bamboo Fiber/Polylactic Acid Composites

by Jianyong Lin, Zexun Yang, Xiaoxia Hu, Gonghua Hong, Shuangbao Zhang and Wei Song

Polymers 2018, 10(4), 403; https://doi.org/10.3390/polym10040403 - 4 Apr 2018

Cited by 83 | Viewed by 5920

Abstract

In this study, a synergistic treatment including dopamine (DA) modification and alkali pretreatment on bamboo fiber (BF) was used as reinforcement in a polylactic acid (PLA) matrix to improve the mechanical and thermal properties of BF/PLA composites. The effects of the sodium hydroxide [...] Read more.

In this study, a synergistic treatment including dopamine (DA) modification and alkali pretreatment on bamboo fiber (BF) was used as reinforcement in a polylactic acid (PLA) matrix to improve the mechanical and thermal properties of BF/PLA composites. The effects of the sodium hydroxide loading rate on the performance of mussel-inspired dopamine-modified bamboo fiber and the BF/PLA composites were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mechanical testing (examining flexural, tensile, and impact properties), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Analysis of the composites suggested that the optimal condition was treatment with a 4 wt % solution of NaOH and a 1 wt % concentration of dopamine. Compared with the untreated bamboo fiber/polylactic acid composites, the synergistic treatment improved the thermal properties and mechanical properties; flexural, tensile, and impact strengths increased by 16.1%, 34.4%, and 3.7%, respectively. It was further verified that appropriate alkali treatment was a promising approach in promoting the effect of dopamine-modified coating while maintaining the crystal structure of the cellulose. Full article

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15 pages, 21886 KiB

Open AccessArticle

Facile and Eco-Friendly Fabrication of Colored and Bioactive Silk Materials Using Silver Nanoparticles Synthesized by Two Flavonoids

by Yuyang Zhou and Ren-Cheng Tang

Polymers 2018, 10(4), 404; https://doi.org/10.3390/polym10040404 - 4 Apr 2018

Cited by 32 | Viewed by 5208

Abstract

Recently, there has been an increasing tendency towards the functionalization of silk using silver nanoparticles (AgNPs) to inhibit bacterial multiplication and disease spread. Considering environmental factors and sustainable development, the preparation of AgNPs using natural extracts is becoming a research hotspot. This study [...] Read more.

Recently, there has been an increasing tendency towards the functionalization of silk using silver nanoparticles (AgNPs) to inhibit bacterial multiplication and disease spread. Considering environmental factors and sustainable development, the preparation of AgNPs using natural extracts is becoming a research hotspot. This study aims at fabricating colored and bioactive silk fabric using AgNPs synthesized by two representative flavonoids (quercetin and rutin). The effects of pH, temperature, and flavonoid concentration on the yield and particle size of AgNPs were studied. The color features and functionalities of the AgNPs-treated silk were also evaluated. The results showed that the AgNPs synthesized by quercetin were generated faster but displayed poorer size uniformity than those prepared by rutin. The as-prepared AgNPs showed good stability. The AgNPs prepared by rutin displayed a more uniform distribution on silk than those synthesized by quercetin. The antibacterial activity of AgNPs-treated silk remained over 90% against E. coli and S. aureus even after 30 washing cycles. The antioxidant activity of the treated silk gradually decreased during washing. The present research proposes a facile and eco-friendly method for the preparation of AgNPs-coated silk material using flavonoids, which can serve as hygiene-related and medical textile materials. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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11 pages, 20113 KiB

Open AccessArticle

Low-Cost Advanced Hydrogels of Calcium Alginate/Carbon Nanofibers with Enhanced Water Diffusion and Compression Properties

by Mar Llorens-Gámez and Ángel Serrano-Aroca

Polymers 2018, 10(4), 405; https://doi.org/10.3390/polym10040405 - 4 Apr 2018

Cited by 44 | Viewed by 7177

Abstract

A series of alginate films was synthesised with several calcium chloride cross-linker contents (from 3 to 18% w/w) with and without a very low amount (0.1% w/w) of carbon nanofibers (CNFs) in order to reduce the production costs as much as [...] Read more.

A series of alginate films was synthesised with several calcium chloride cross-linker contents (from 3 to 18% w/w) with and without a very low amount (0.1% w/w) of carbon nanofibers (CNFs) in order to reduce the production costs as much as possible. The results of this study showed a very significant enhancement of liquid water diffusion and mechanical compressive modulus for high calcium chloride contents when this minuscule amount of CNFs is incorporated into calcium alginate hydrogels. These excellent results are attributed to a double cross-linking process, in which calcium cations are capable of cross-linking both alginate chains and CNFs creating a reinforced structure exhibiting ultrafast water diffusion through carbon nanochannels. Thus, these excellent results render these new alginate composites very promising for many bioengineering fields in need of low-cost advanced hydrogels with superior water diffusion and compression properties. Full article

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14 pages, 45513 KiB

Open AccessArticle

Crystalline Modification and Its Effects on Dielectric Breakdown Strength and Space Charge Behavior in Isotactic Polypropylene

by Ling Zhang, Yunxiao Zhang, Yuanxiang Zhou, Chenyuan Teng, Zhaowei Peng and Stephen Spinella

Polymers 2018, 10(4), 406; https://doi.org/10.3390/polym10040406 - 5 Apr 2018

Cited by 20 | Viewed by 4525

Abstract

Adding nucleating agents (NAs) is one of the most efficient ways to obtain improved mechanical, optical, and thermal properties of isotactic polypropylene (iPP). While it is well appreciated that electrical property is critically affected by crystalline modification, the role between them remains unclear. [...] Read more.

Adding nucleating agents (NAs) is one of the most efficient ways to obtain improved mechanical, optical, and thermal properties of isotactic polypropylene (iPP). While it is well appreciated that electrical property is critically affected by crystalline modification, the role between them remains unclear. Here, we address this issue by incorporating commercial α-NA and β-NA into iPP, both of which exhibit strong nucleation ability, e.g., reducing the size of crystalline agglomerates from 45.3 μm (Pure-iPP) to 2.5 μm (α-iPP) and 7.6 μm (β-iPP), respectively. Mechanical testing results show that while β-modification decreases the tensile strength a little, it does enhance the elongation at break (200%) and toughness (25.3% higher), relative to its unfilled counterparts. Moreover, a well-dispersed β-iPP system obtains a comprehensive improvement of electrical properties, including dielectric breakdown strength, space charge suppression, and internal field distortion under a high external field (−100 kV/mm) due to newly-generated deep charge trapping sites. This crystalline modification strategy is attractive for future development of many engineering insulating polymers. Full article

(This article belongs to the Special Issue Phase Behavior in Polymers)

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12 pages, 38268 KiB

Open AccessArticle

Polyethylene-Grafted Gold and Silver Nanoparticles Using Catalyzed Chain Growth (CCG)

by Jannik Wagner, Wentao Peng and Philipp Vana

Polymers 2018, 10(4), 407; https://doi.org/10.3390/polym10040407 - 6 Apr 2018

Cited by 8 | Viewed by 6599

Abstract

We report an efficient synthesis route for the formation of gold/silver-core–PE-shell nanohybrids in a simple self-assembly approach using PE with strong aurophilicity and argentophilicity, via thiol- and trithiocarbonate terminated moieties. This united the unique properties of polyethylene (PE) with gold and silver nanoparticles, [...] Read more.

We report an efficient synthesis route for the formation of gold/silver-core–PE-shell nanohybrids in a simple self-assembly approach using PE with strong aurophilicity and argentophilicity, via thiol- and trithiocarbonate terminated moieties. This united the unique properties of polyethylene (PE) with gold and silver nanoparticles, using the well-defined end-group design of PE. These nanocomposites showed a similar solubility as PE, as confirmed by dynamic light scattering, and could be fully incorporated into a polyethylene matrix with different particle contents, as visualized by transmission electron microscopy. Using UV/vis-spectroscopy, we observed reversible, thermoresponsive aggregation/deaggregation properties in the nanohybrids, validating the strong and effective anchoring of PE on gold/silver surfaces. Full article

(This article belongs to the Special Issue Polymerizations from Surfaces)

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16 pages, 18984 KiB

Open AccessArticle

Active Ester Containing Surfmer for One-Stage Polymer Nanoparticle Surface Functionalization in Mini-Emulsion Polymerization

by Vanessa L. Albernaz, Monika Bach, Achim Weber, Alexander Southan and Günter E. M. Tovar

Polymers 2018, 10(4), 408; https://doi.org/10.3390/polym10040408 - 6 Apr 2018

Cited by 8 | Viewed by 8994

Abstract

Functional surface active monomers (surfmers) are molecules that combine the functionalities of surface activity, polymerizability, and reactive groups. This study presents an improved pathway for the synthesis of the active ester containing surfmer p-(11-acrylamido)undecanoyloxyphenyl dimethylsulfonium methyl sulfate (AUPDS). Further, the preparation of [...] Read more.

Functional surface active monomers (surfmers) are molecules that combine the functionalities of surface activity, polymerizability, and reactive groups. This study presents an improved pathway for the synthesis of the active ester containing surfmer p-(11-acrylamido)undecanoyloxyphenyl dimethylsulfonium methyl sulfate (AUPDS). Further, the preparation of poly(methyl methacrylate) and polystyrene nanoparticles (NPs) by mini-emulsion polymerization using AUPDS is investigated, leading to NPs with active ester groups on their surface. By systematically varying reaction parameters and reagent concentrations, it was found that AUPDS feed concentrations between 2–4 mol% yielded narrowly distributed and stable spherical particles with average sizes between 83 and 134 nm for non-cross-linked NPs, and up to 163 nm for cross-linked NPs. By basic hydrolysis of the active ester groups in aqueous dispersion, the positive ζ-potential (ZP) was converted into a negative ZP and charge quantities determined by polyelectrolyte titrations before and after hydrolysis were in the same range, indicating that the active ester groups were indeed accessible in aqueous suspension. Increasing cross-linker amounts over 10 mol% also led to a decrease of ZP of NPs, probably due to internalization of the AUPDS during polymerization. In conclusion, by using optimized reaction conditions, it is possible to prepare active ester functionalized NPs in one stage using AUPDS as a surfmer in mini-emulsion polymerization. Full article

(This article belongs to the Special Issue Selected Papers from "ECIS 2017")

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12 pages, 4079 KiB

Open AccessArticle

Effect of SiO₂ Content on the Extended Creep Behavior of SiO₂-Based Wood-Inorganic Composites Derived via the Sol–Gel Process Using the Stepped Isostress Method

by Ke-Chang Hung and Jyh-Horng Wu

Polymers 2018, 10(4), 409; https://doi.org/10.3390/polym10040409 - 6 Apr 2018

Cited by 13 | Viewed by 4122

Abstract

In this study, methyltrimethoxysilane (MTMOS) was used as a reagent to prepare SiO₂-based wood-inorganic composites (WIC_SiO₂) via the sol-gel process, and subsequently, the extended creep behaviors of WIC_SiO₂ with weight percent gains (WPGs) of 10%, 20%, [...] Read more.

In this study, methyltrimethoxysilane (MTMOS) was used as a reagent to prepare SiO₂-based wood-inorganic composites (WIC_SiO₂) via the sol-gel process, and subsequently, the extended creep behaviors of WIC_SiO₂ with weight percent gains (WPGs) of 10%, 20%, and 30% were estimated using the stepped isostress method (SSM). The results revealed that the density of all samples ranged from 426 to 513 kg/m³, and no significant difference in the modulus of elasticity (MOE) was noted among all of the samples (10.5–10.7 GPa). However, the MOR of WIC_SiO₂ with a WPG of 20% (102 MPa) was significantly greater than that of untreated wood (87 MPa). In addition, according to the result using the SSM, the SSM-predicted creep master curve fitted well with the experimental data for the untreated wood and WIC_SiO₂. This result demonstrated that the SSM could be a useful method to evaluate long-term creep behaviors of wood and WIC_SiO₂. Furthermore, the activation volume (V*) of the specimens was calculated from the linear slope of Eyring plots, and the resulting V* of all of the WIC_SiO₂ (0.754–0.842 nm³) was lower than that of untreated wood (0.856 nm³). On the other hand, the modulus reduction of untreated wood showed 39%, 45%, 48%, and 51% at 5, 15, 30, and 50 years, respectively. In contrast, the modulus reduction of the WIC_SiO₂ with a WPG of 10% decreased to 25%, 31%, 35%, and 38% at 5, 15, 30, and 50 years, respectively. Similar trends were also observed for other WIC_SiO₂ with different WPGs. Of these, the WIC_SiO₂ with a WPG of 20% exhibited the lowest reduction in time-dependent modulus (31%) over a 50-year period. Accordingly, the creep resistance of the wood could be effectively enhanced under the MTMOS treatment. Full article

(This article belongs to the Special Issue Modification of Natural Fibres to Improve Biocomposites Performances)

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14 pages, 21349 KiB

Open AccessArticle

Low-Dissipation Thermosets Derived from Oligo(2,6-Dimethyl Phenylene Oxide)-Containing Benzoxazines

by Chien-Han Chen, Kuan-Wei Lee, Ching-Hsuan Lin and Tzong-Yuan Juang

Polymers 2018, 10(4), 411; https://doi.org/10.3390/polym10040411 - 7 Apr 2018

Cited by 17 | Viewed by 6819

Abstract

Poly(2,6-dimethyl phenyl oxide) (PPO) is known for its low dissipation factor. To achieve insulating materials with low dissipation factors for high-frequency communication applications, a telechelic oligomer-type benzoxazine (P-APPO) and a main-chain type benzoxazine polymer (BPA-APPO) were prepared from an amine end-capped oligo (2,6-dimethyl [...] Read more.

Poly(2,6-dimethyl phenyl oxide) (PPO) is known for its low dissipation factor. To achieve insulating materials with low dissipation factors for high-frequency communication applications, a telechelic oligomer-type benzoxazine (P-APPO) and a main-chain type benzoxazine polymer (BPA-APPO) were prepared from an amine end-capped oligo (2,6-dimethyl phenylene oxide) (APPO). The APPO was prepared from a nucleophilic substitution of a phenol-end capped oligo (2,6-dimethyl phenylene oxide) (a commercial product, SA 90) with fluoronitrobenzene, and followed by catalytic hydrogenation. After self-curing or curing with a dicyclopentadiene-phenol epoxy (HP 7200), thermosets with high-T_g and low-dissipation factor can be achieved. Furthermore, the resulting epoxy thermosets show better thermal and dielectric properties than those of epoxy thermoset cured from its precursor SA90, demonstrating it is a successful modification in simultaneously enhancing the thermal and dielectric properties. Full article

(This article belongs to the Special Issue New Developments in Ring-Opening Polymerization)

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18 pages, 10012 KiB

Open AccessArticle

How Glycerol and Water Contents Affect the Structural and Functional Properties of Starch-Based Edible Films

by Ewelina Basiak, Andrzej Lenart and Frédéric Debeaufort

Polymers 2018, 10(4), 412; https://doi.org/10.3390/polym10040412 - 8 Apr 2018

Cited by 229 | Viewed by 19685

Abstract

As starch is an inexpensive, filmogenic, easily processable and a widely available material, it is a material that can be utilized in the creation of biodegradable films and containers, presenting as a viable alternative to polymers derived from petrol. Moreover, starch could also [...] Read more.

As starch is an inexpensive, filmogenic, easily processable and a widely available material, it is a material that can be utilized in the creation of biodegradable films and containers, presenting as a viable alternative to polymers derived from petrol. Moreover, starch could also be used to create edible coatings for fresh foods in order to extend shelf life. As such, wheat starch films with two glycerol contents were formulated to mimic the effects of compounds currently used to coat fruit. Their structural and functional properties were characterized. This study found that the transfer properties of starch films containing 33% of plasticizer was less effective than film comprised of 50% glycerol. Water diffusivity, oxygen permeability, and water vapor permeability at two different humidity gradients, surface tension, works of surface adhesion and cohesion, and moisture sorption were tested. Glycerol content does not play a significant role on the color or mechanical properties. This work shows that glycerol can strongly affect the functional properties of starch-based coatings and films. Full article

(This article belongs to the Collection Polysaccharides)

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14 pages, 35068 KiB

Open AccessArticle

Experimental Study of the Effect of Internal Defects on Stress Waves during Automated Fiber Placement

by Zhenyu Han, Shouzheng Sun, Wenqi Li, Yaoxu Zhao and Zhongxi Shao

Polymers 2018, 10(4), 413; https://doi.org/10.3390/polym10040413 - 9 Apr 2018

Cited by 24 | Viewed by 4396

Abstract

The detection technique of component defects is currently only realized to detect offline defects and online surface defects during automated fiber placement (AFP). The characteristics of stress waves can be effectively applied to identify and detect internal defects in material structure. However, the [...] Read more.

The detection technique of component defects is currently only realized to detect offline defects and online surface defects during automated fiber placement (AFP). The characteristics of stress waves can be effectively applied to identify and detect internal defects in material structure. However, the correlation mechanism between stress waves and internal defects remains unclear during the AFP process. This paper proposes a novel experimental method to test stress waves, where continuous loading induced by process itself is used as an excitation source without other external excitation. Twenty-seven groups of thermosetting prepreg laminates under different processing parameters are manufactured to obtain different void content. In order to quantitatively estimate the void content in the prepreg structure, the relation model between the void content and ultrasonic attenuation coefficient is revealed using an A-scan ultrasonic flaw detector and photographic methods by optical microscope. Furthermore, the high-frequency noises of stress waves are removed using Haar wavelet transform. The peaks, the Manhattan distance and mean stress during the laying process are analyzed and evaluated. Partial conclusions in this paper could provide theoretical support for online real-time detection of internal defects based on stress wave characteristics. Full article

(This article belongs to the Special Issue Polymer Hybrids and Composites)

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10 pages, 20123 KiB

Open AccessCommunication

Huge Enhancement of Luminescence from a Coaxial-Like Heterostructure of Poly(3-methylthiophene) and Au

by Bo-Hyun Kim, Hojin Lee, Do Hyoung Kim, Seokho Kim, Jinho Choi, Gil Sun Lee, Dong Hyuk Park and Sunjong Lee

Polymers 2018, 10(4), 414; https://doi.org/10.3390/polym10040414 - 9 Apr 2018

Viewed by 3632

Abstract

Recently, the light-matter interaction at nanoscale has attracted great interest from physicists, chemists and material scientists, as it gives peculiar optical properties that couldn’t be observed at the bulk scale. The synthesis and characterization of organic-inorganic heterostructures forming quantum dots, nanowires or nanotubes [...] Read more.

Recently, the light-matter interaction at nanoscale has attracted great interest from physicists, chemists and material scientists, as it gives peculiar optical properties that couldn’t be observed at the bulk scale. The synthesis and characterization of organic-inorganic heterostructures forming quantum dots, nanowires or nanotubes provide opportunities to understand their photophysical mechanism and to apply optoelecronic devices. Herein, we report a huge enhanced luminescence in a coaxial-like heterostructured poly (3-methylthiophene) (P3MT) with Au. We electrochemically synthesized P3MT nanowires (NWs) on a nanoporous template, and sequentially deposited Au on the surface of P3MT NWs. The diameter of heterostructured P3MT/Au NWs was about 200 nm, where the cladding-shape Au were about 10 nm. The visible range absorbance, with two new absorption peaks of P3MT/Au NWs, was significantly increased compared with that of P3MT NWs. Accordingly, the photoluminescence (PL) of a P3MT/Au NW was enormously increased; up to 170 times compared to that of P3MT NWs. More interestingly, an unexpected enhancement of PL was observed from cross-junction point of P3MT/Au NWs. The abnormal PL properties of P3MT/Au NWs were attributed to the charge transfer and the surface plasmon resonance between the cladding-shape Au and the core-shape P3MT, which resulted in the enhanced quantum yield. This incites us to reconsider the light-matter interaction in polymer-metal hybrid structures applicable for high-performance optoelectronic devices. Full article

(This article belongs to the Special Issue Polymeric Materials for Optical Applications)

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13 pages, 47371 KiB

Open AccessArticle

Fabrication and In Vitro Characterization of Electrochemically Compacted Collagen/Sulfated Xylorhamnoglycuronan Matrix for Wound Healing Applications

by Lingzhi Kang, Xiao Liu, Zhilian Yue, Zhi Chen, Chris Baker, Pia C. Winberg and Gordon G. Wallace

Polymers 2018, 10(4), 415; https://doi.org/10.3390/polym10040415 - 9 Apr 2018

Cited by 23 | Viewed by 6798

Abstract

Skin autografts are in great demand due to injuries and disease, but there are challenges using live tissue sources, and synthetic tissue is still in its infancy. In this study, an electrocompaction method was applied to fabricate the densely packed and highly ordered [...] Read more.

Skin autografts are in great demand due to injuries and disease, but there are challenges using live tissue sources, and synthetic tissue is still in its infancy. In this study, an electrocompaction method was applied to fabricate the densely packed and highly ordered collagen/sulfated xylorhamnoglycuronan (SXRGlu) scaffold which closely mimicked the major structure and components in natural skin tissue. The fabricated electrocompacted collagen/SXRGlu matrices (ECLCU) were characterized in terms of micromorphology, mechanical property, water uptake ability and degradability. The viability, proliferation and morphology of human dermal fibroblasts (HDFs) cells on the fabricated matrices were also evaluated. The results indicated that the electrocompaction process could promote HDFs proliferation and SXRGlu could improve the water uptake ability and matrices’ stability against collagenase degradation, and support fibroblast spreading on the ECLCU matrices. Therefore, all these results suggest that the electrocompacted collagen/SXRGlu scaffold is a potential candidate as a dermal substitute with enhanced biostability and biocompatibility. Full article

(This article belongs to the Special Issue Protein Biopolymer)

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13 pages, 3877 KiB

Open AccessCommunication

In Situ Raman Spectroscopy as a Tool for Structural Insight into Cation Non-Ionomeric Polymer Interactions during Ion Transport

by Krzysztof Artur Bogdanowicz, Domenico Pirone, Judit Prats-Reig, Veronica Ambrogi, José Antonio Reina and Marta Giamberini

Polymers 2018, 10(4), 416; https://doi.org/10.3390/polym10040416 - 9 Apr 2018

Cited by 9 | Viewed by 4571

Abstract

Low-modified liquid-crystalline polyether (CP36), as a model compound, was synthesised with the purpose of preparing a membrane with columnar ionic channels. A free-standing cation permselective biomimetic membrane was successfully prepared and found to have channels made of polymeric columns homeotropically oriented, which was [...] Read more.

Low-modified liquid-crystalline polyether (CP36), as a model compound, was synthesised with the purpose of preparing a membrane with columnar ionic channels. A free-standing cation permselective biomimetic membrane was successfully prepared and found to have channels made of polymeric columns homeotropically oriented, which was confirmed in X-ray diffraction (XRD) analysis. A first insight into a real-time interaction between two selected cations: H⁺ and Na⁺, and polyether during transport through the polymeric membrane was demonstrated using joined chronoamperometry and Raman spectroscopy techniques. Raman studies unveiled the possibility for smaller protons to bypass the usual ionic pathway via polyetheric chain and use outer part of ionic channel for conduction thanks to ester bonds. Full article

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11 pages, 8326 KiB

Open AccessArticle

Selenide-Containing Polyimides with an Ultrahigh Intrinsic Refractive Index

by Qilong Li, Jiandong Zhang, Xiangqiang Pan, Zhengbiao Zhang, Jian Zhu and Xiulin Zhu

Polymers 2018, 10(4), 417; https://doi.org/10.3390/polym10040417 - 9 Apr 2018

Cited by 23 | Viewed by 5317

Abstract

This work developed novel selenium-containing polyimides with a high intrinsic refractive index. Four polyimides with different selenium contents and repeat unit structures were designed and synthesized via amine-dianhydride polycondensation of one of two diamines, i.e., 4,4′-oxydianiline or bis(4-aminophenyl)selanide, with one of two [...] Read more.

This work developed novel selenium-containing polyimides with a high intrinsic refractive index. Four polyimides with different selenium contents and repeat unit structures were designed and synthesized via amine-dianhydride polycondensation of one of two diamines, i.e., 4,4′-oxydianiline or bis(4-aminophenyl)selanide, with one of two dianhydrides, i.e., bis(4-(3,4-dicarboxylbenzoyloxy)phenyl) ester dianhydride or 1,1′-bis(4-(3,4-dicarboxylbenzoyloxy)phenyl) selenide dianhydride. Various techniques, e.g., nuclear magnetic resonance, Fourier transformed infrared spectroscopy, and wide-angle X-ray diffraction, were used to characterize the polymers’ structures. Differential scanning calorimetry, thermogravimetric analysis, ultraviolet-visible spectroscopy, and spectroscopic ellipsometry were used to characterize the properties of the polymers. The selenium contents showed a positive effect on the refractive index of the final polymer. In addition, the refractive index can reach up to 1.968 at 633 nm, which was the highest intrinsic refractive index of a polyimide ever reported. Because of the high intrinsic refractive index, the reflective ratio of visible light on the surface of a silicon wafer was significantly reduced, indicating the potentially utility of the polymer in an anti-reflection coating. Full article

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15 pages, 15278 KiB

Open AccessArticle

Preliminary Structural Characteristics of Polysaccharides from Pomelo Peels and Their Antitumor Mechanism on S180 Tumor-Bearing Mice

by Juan Yu, Haiyu Ji and Anjun Liu

Polymers 2018, 10(4), 419; https://doi.org/10.3390/polym10040419 - 9 Apr 2018

Cited by 24 | Viewed by 6334

Abstract

In this study, the polysaccharides (PPs) from pomelo peels were investigated for their structural characteristics and antitumor mechanism on sarcoma S180-bearing mice. Components, FT-IR, and GC analysis showed that PPs, mainly composed of glucose, were typical acid polysaccharides with α-d-pyranoid glucose [...] Read more.

In this study, the polysaccharides (PPs) from pomelo peels were investigated for their structural characteristics and antitumor mechanism on sarcoma S180-bearing mice. Components, FT-IR, and GC analysis showed that PPs, mainly composed of glucose, were typical acid polysaccharides with α-d-pyranoid glucose containing 74.52% carbohydrate and 16.33% uronic acid. The in vivo antitumor tests revealed that PPs could effectively suppress the transplanted S180 tumors growth, as well as protect the immune organs, improve proliferation ability of splenic lymphocytes and killing activity of NK cells in tumor-bearing mice. Furthermore, the levels of serum cytokines (IL-2, IFN-γ and TNF-α) and the proportion of CD4⁺ T cells in peripheral blood of mice bearing S180 tumors were also significantly increased after treatment with PPs. Meanwhile, the transplanted S180 tumor cells exhibited obvious apoptotic phenotype after PPs treatment by arresting the cell cycle in S phase, down-regulating the Bcl-2 expressions and up-regulating the Bax levels. These data showed that PPs were mainly composed of glucose with α-d-pyranoid ring and could induce apoptosis of solid tumor cells by enhancing the antitumor immunity of tumor-bearing mice, which would provide a theoretical basis for the practical application in food and medical industries. Full article

(This article belongs to the Collection Polysaccharides)

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20 pages, 52323 KiB

Open AccessArticle

Effect of Polysiloxanes on Roughness and Durability of Basalt Fibres–Reinforced Cement Mortar

by Danuta Barnat-Hunek, Grzegorz Łagód, Stanisław Fic and Monika Jarosz-Hadam

Polymers 2018, 10(4), 420; https://doi.org/10.3390/polym10040420 - 9 Apr 2018

Cited by 24 | Viewed by 4259

Abstract

The influence of roughness and the way it affects the adhesion properties and surface free energy (SFE) of polysiloxanes hydrophobised basalt fibres–reinforced cement mortars were determined in this article. The physical properties of mortars were investigated in the experimental part, which also explored [...] Read more.

The influence of roughness and the way it affects the adhesion properties and surface free energy (SFE) of polysiloxanes hydrophobised basalt fibres–reinforced cement mortars were determined in this article. The physical properties of mortars were investigated in the experimental part, which also explored the impact of hydrophobisation and basalt fibres (BF) addition on SFE, frost resistance, contact angle (CA), and roughness. A device capable of calculating all parameters was used to indicate the surface roughness and 3D topography. Prior to and after conducting surface and weight hydrophobisation, the contact angle of mortars was specified. Subsequently, it was used for carrying out SFE calculation by means of Neumann’s method, enabling us to characterize the adhesion properties and wettability of mortars. The research indicated that the surface roughness was substantially decreased, in turn raising the frost resistance. The corrosion resistance drops when the surface roughness, water absorption, and number of fibres in the mortar increase. The SEM images presenting the structure of polysiloxane coating and mortars were provided. Full article

(This article belongs to the Special Issue Siloxane-Based Polymers)

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16 pages, 25907 KiB

Open AccessArticle

The Influence of Accelerated UV-A and Q-SUN Irradiation on the Antibacterial Properties of Hydrophobic Coatings Containing Eucomis comosa Extract

by Małgorzata Mizielińska, Urszula Kowalska, Piotr Salachna, Łukasz Łopusiewicz and Michał Jarosz

Polymers 2018, 10(4), 421; https://doi.org/10.3390/polym10040421 - 9 Apr 2018

Cited by 7 | Viewed by 4549

Abstract

The purpose of this research was to examine the antimicrobial properties against Gram-positive bacteria, as well as the water vapour characteristic of polylactic acid (PLA) films covered with a methyl–hydroxypropyl–cellulose (MHPC)/cocoa butter carrier containing Eucomis comosa extract as an active substance. The second [...] Read more.

The purpose of this research was to examine the antimicrobial properties against Gram-positive bacteria, as well as the water vapour characteristic of polylactic acid (PLA) films covered with a methyl–hydroxypropyl–cellulose (MHPC)/cocoa butter carrier containing Eucomis comosa extract as an active substance. The second purpose of the study was to evaluate the influence of accelerated UV-A and Q-SUN irradiation (UV-aging) on the antimicrobial properties and the barrier characteristic of the coatings. The results of the study revealed that MHPC/cocoa butter coatings had no influence on the growth of Staphylococcus aureus, Bacillus cereus, and Bacillus atrophaeus. MHPC/cocoa butter coatings containing E. comosa extract reduced the number of bacterial strains. MHPC/cocoa butter coatings also decreased the water vapour permeability of PLA. It was shown that accelerated UV-A and Q-SUN irradiations altered the chemical composition of the coatings containing cocoa butter. Despite the alteration of the chemical composition of the layers, the accelerated Q-SUN and UV-A irradiation had no influence on the antimicrobial properties of E. comosa extract coatings against S. aureus and B. cereus. It was found that only Q-SUN irradiation decreased the coating activity with an extract against B. atrophaeus, though this was to a small degree. Full article

(This article belongs to the Special Issue Antimicrobial Polymer-Based Materials for Food Packaging Applications)

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14 pages, 14305 KiB

Open AccessArticle

A Study of the Polycondensation of (Tetrahydroxy)(Tetraaryl)Cyclotetrasiloxanes under Equilibrium and Non-Equilibrium Conditions in the Presence and Absence of Montmorillonite

by Nataliya N. Makarova, Yury I. Lyakhovetsky, Irina M. Petrova, Fedor M. Dolgushin, Nikolai S. Ikonnikov, Alexander S. Peregudov, Tatyana V. Strelkova and Zinaida S. Klemenkova

Polymers 2018, 10(4), 422; https://doi.org/10.3390/polym10040422 - 9 Apr 2018

Cited by 3 | Viewed by 3873

Abstract

Oligo- and polycyclosiloxanes were obtained by the polycondensation of (tetrahydroxy)(tetraaryl)cyclotetrasiloxanes in equilibrium and non-equilibrium conditions in the presence and absence of montmorillonite (MMT). Their composition and the structures of their components were investigated by infrared (IR) spectroscopy, ²⁹Si nuclear magnetic resonance (NMR) [...] Read more.

Oligo- and polycyclosiloxanes were obtained by the polycondensation of (tetrahydroxy)(tetraaryl)cyclotetrasiloxanes in equilibrium and non-equilibrium conditions in the presence and absence of montmorillonite (MMT). Their composition and the structures of their components were investigated by infrared (IR) spectroscopy, ²⁹Si nuclear magnetic resonance (NMR) spectroscopy, atmospheric pressure chemical ionization (APCI) mass spectrometry, powder X-ray diffraction (XRD), and gel-penetrating chromatography (GPC). Also, a comparison of polymers formed in the presence of MMT and via anionic polymerization was performed showing differences in their structures. Full article

(This article belongs to the Special Issue Precision Polymer Synthesis)

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12 pages, 10002 KiB

Open AccessArticle

KnowVolution of the Polymer-Binding Peptide LCI for Improved Polypropylene Binding

by Kristin Rübsam, Mehdi D. Davari, Felix Jakob and Ulrich Schwaneberg

Polymers 2018, 10(4), 423; https://doi.org/10.3390/polym10040423 - 10 Apr 2018

Cited by 51 | Viewed by 7592

Abstract

The functionalization of polymer surfaces by polymer-binding peptides offers tremendous opportunities for directed immobilization of enzymes, bioactive peptides, and antigens. The application of polymer-binding peptides as adhesion promoters requires reliable and stable binding under process conditions. Molecular modes of interactions between material surfaces, [...] Read more.

The functionalization of polymer surfaces by polymer-binding peptides offers tremendous opportunities for directed immobilization of enzymes, bioactive peptides, and antigens. The application of polymer-binding peptides as adhesion promoters requires reliable and stable binding under process conditions. Molecular modes of interactions between material surfaces, peptides, and solvent are often not understood to an extent that enables (semi-) rational design of polymer-binding peptides, hindering the full exploitation of their potential. Knowledge-gaining directed evolution (KnowVolution) is an efficient protein engineering strategy that facilitates tailoring protein properties to application demands through a combination of directed evolution and computational guided protein design. A single round of KnowVolution was performed to gain molecular insights into liquid chromatography peak I peptide, 47 aa (LCI)-binding to polypropylene (PP) in the presence of the competing surfactant Triton X-100. KnowVolution yielded a total of 8 key positions (D19, S27, Y29, D31, G35, I40, E42, and D45), which govern PP-binding in the presence of Triton X-100. The recombination of two of the identified amino acid substitutions (Y29R and G35R; variant KR-2) yielded a 5.4 ± 0.5-fold stronger PP-binding peptide compared to LCI WT in the presence of Triton X-100 (1 mM). The LCI variant KR-2 shows a maximum binding capacity of 8.8 ± 0.1 pmol/cm² on PP in the presence of Triton X-100 (up to 1 mM). The KnowVolution approach enables the development of polymer-binding peptides, which efficiently coat and functionalize PP surfaces and withstand surfactant concentrations that are commonly used, such as in household detergents. Full article

(This article belongs to the Special Issue Polypeptide Containing Polymers)

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22 pages, 44597 KiB

Open AccessArticle

Morphology, Nucleation, and Isothermal Crystallization Kinetics of Poly(Butylene Succinate) Mixed with a Polycarbonate/MWCNT Masterbatch

by Thandi P. Gumede, Adriaan S. Luyt, Ricardo A. Pérez-Camargo, Agnieszka Tercjak and Alejandro J. Müller

Polymers 2018, 10(4), 424; https://doi.org/10.3390/polym10040424 - 10 Apr 2018

Cited by 15 | Viewed by 5080

Abstract

In this study, nanocomposites were prepared by melt blending poly(butylene succinate) (PBS) with a polycarbonate (PC)/multi-wall carbon nanotubes (MWCNTs) masterbatch, in a twin-screw extruder. The nanocomposites contained 0.5, 1.0, 2.0, and 4.0 wt% MWCNTs. Differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) [...] Read more.

In this study, nanocomposites were prepared by melt blending poly(butylene succinate) (PBS) with a polycarbonate (PC)/multi-wall carbon nanotubes (MWCNTs) masterbatch, in a twin-screw extruder. The nanocomposites contained 0.5, 1.0, 2.0, and 4.0 wt% MWCNTs. Differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) results indicate that the blends are partially miscible, hence they form two phases (i.e., PC-rich and PBS-rich phases). The PC-rich phase contained a small amount of PBS chains that acted as a plasticizer and enabled crystallization of the PC component. In the PBS-rich phase, the amount of the PC chains present gave rise to increases in the glass transition temperature of the PBS phase. The presence of two phases was supported by scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis, where most MWCNTs aggregated in the PC-rich phase (especially at the high MWCNTs content of 4 wt%) and a small amount of MWCNTs were able to diffuse to the PBS-rich phase. Standard DSC scans showed that the MWCNTs nucleation effects saturated at 0.5 wt% MWCNT content on the PBS-rich phase, above this content a negative nucleation effect was observed. Isothermal crystallization results indicated that with 0.5 wt% MWCNTs the crystallization rate was accelerated, but further increases in MWCNTs loading (and also in PC content) resulted in progressive decreases in crystallization rate. The results are explained by increased MWCNTs aggregation and reduced diffusion rates of PBS chains, as the masterbatch content in the blends increased. Full article

(This article belongs to the Special Issue Polymer Hybrids and Composites)

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13 pages, 2597 KiB

Open AccessArticle

Novel Nano-Liposome Formulation for Dry Eyes with Components Similar to the Preocular Tear Film

by Marta Vicario-de-la-Torre, María Caballo-González, Eva Vico, Laura Morales-Fernández, Pedro Arriola-Villalobos, Beatriz De las Heras, José Manuel Benítez-del-Castillo, Manuel Guzmán, Thomas Millar, Rocío Herrero-Vanrell and Irene T. Molina-Martínez

Polymers 2018, 10(4), 425; https://doi.org/10.3390/polym10040425 - 11 Apr 2018

Cited by 32 | Viewed by 5859

Abstract

Dry eye is commonly treated with artificial tears; however, developing artificial tears similar to natural tears is difficult due to the complex nature of tears. We characterized and evaluated a novel artificial tear formulation with components similar to the lipid and aqueous constituents [...] Read more.

Dry eye is commonly treated with artificial tears; however, developing artificial tears similar to natural tears is difficult due to the complex nature of tears. We characterized and evaluated a novel artificial tear formulation with components similar to the lipid and aqueous constituents of natural tears. Nano-liposomes, composed in part of phosphatidylcholine, were dispersed in an aqueous solution of bioadhesive sodium hyaluronate. Liposome size, zeta potential, and physicochemical properties of the fresh and stored (4 °C) liposomal formulation were analyzed. In vitro tolerance was tested using human corneal and conjunctival cell lines by exposures of 15 min to 4 h. The tolerance of the liposomal formulation was evaluated in animals (rabbits). The average liposome size was 186.3 ± 7.0 nm, and the zeta potential was negative. The osmolarity of the formulation was 198.6 ± 1.7 mOsm, with a surface tension of 36.5 ± 0.4 mN/m and viscosity of 3.05 ± 0.02 mPa·s. Viability values in the human corneal and conjunctival cell lines were always >80%, even after liposomal formulation storage for 8 weeks. Discomfort and clinical signs after instillation in rabbit eyes were absent. The new formulation, based on phosphatidylcholine-liposomes dispersed in sodium hyaluronate has suitable components and characteristics, including high in vitro cell viability and good in vivo tolerance, to serve as a tear substitute. Full article

(This article belongs to the Special Issue Selected Papers from "ECIS 2017")

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18 pages, 23068 KiB

Open AccessArticle

A Numerical Method Charactering the Electromechanical Properties of Particle Reinforced Composite Based on Statistics

by Mengzhou Chang and Zhenqing Wang

Polymers 2018, 10(4), 426; https://doi.org/10.3390/polym10040426 - 11 Apr 2018

Cited by 6 | Viewed by 3590

Abstract

A novel model for a network of polymer chains is proposed considering the distribution of polymer chains inside the composite in this work. Some factors that influence the distribution of polymer chains are quantitatively investigated, such as external surface geometry, internal filler, and [...] Read more.

A novel model for a network of polymer chains is proposed considering the distribution of polymer chains inside the composite in this work. Some factors that influence the distribution of polymer chains are quantitatively investigated, such as external surface geometry, internal filler, and local deformation. Furthermore, the Maxwell stress induced by an electric field is characterized by the statistics of local charge density, as the basic analyzing electromechanical properties of materials. In particular, taking the non-uniform distribution of polymer chains into account, the electromechanical properties of two materials—VHB 4910 and CaCu₃Ti₄O₁₂-polydimethylsiloxane (CCTO-PDMS)—are investigated to validate the applicability of the proposed model. The comparison between simulation results and experimental results from existing literature shows that the model was successfully employed to predict the electromechanical properties of polymer composites. Full article

(This article belongs to the Special Issue Simulations of Polymers)

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16 pages, 16703 KiB

Open AccessArticle

Donor-Acceptor-Type Copolymers Based on 3,4-Propylenedioxy-thiophene and 5,6-Difluorobenzotriazole: Synthesis and Electrochromic Properties

by Fanda Feng, Lingqian Kong, Hongmei Du, Jinsheng Zhao and Junhong Zhang

Polymers 2018, 10(4), 427; https://doi.org/10.3390/polym10040427 - 11 Apr 2018

Cited by 15 | Viewed by 4278

Abstract

Three solution-processable D-A-type conjugated polymers P1, P2 and P3 were successfully synthesized via the Pd-catalyzed Stille cross-coupling copolymerization approach, with 6,8-Dibromo-3,3-bis-decyl-3,4-dihydro-2H-thieno[3,4-b][1,4] dioxepine (M1) and 2,5-Bis(trimethylstannanyl)thiophene (M3) as the donor units and 4,7-Dibromo-5,6-difluoro-2-(2-hexyl-decyl)-2H-benzotriazole (M2) as the acceptor [...] Read more.

Three solution-processable D-A-type conjugated polymers P1, P2 and P3 were successfully synthesized via the Pd-catalyzed Stille cross-coupling copolymerization approach, with 6,8-Dibromo-3,3-bis-decyl-3,4-dihydro-2H-thieno[3,4-b][1,4] dioxepine (M1) and 2,5-Bis(trimethylstannanyl)thiophene (M3) as the donor units and 4,7-Dibromo-5,6-difluoro-2-(2-hexyl-decyl)-2H-benzotriazole (M2) as the acceptor unit, wherein the feed ratio of the three units was 1:3:4 (M1:M2:M3, the same below), 1:1:2 and 3:1:4 for P1, P2, and P3, respectively. The results obtained by our test showed that the feed ratio between the D and A units had a significant effect on both the electrochemical and the spectroelectrochemical properties of the three polymers. The copolymers exhibited a gradually deepening red color in neutral state with the increase of M1 content and then turned to a transmissive grey color in the oxidation state. Also, three copolymers showed good performance in electrochromic parameters, which mainly consists of optical contrast, response time, and coloration efficiency. In general, the excellent electrochromic performances of the copolymers make them outstanding candidates for electrochromic material applications. Full article

(This article belongs to the Special Issue π-Stacked Polymers)

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12 pages, 2261 KiB

Open AccessArticle

Influence of Polycation Composition on Electrochemical Film Formation

by Sabine Schneider, Corinna Janssen, Elisabeth Klindtworth, Olga Mergel, Martin Möller and Felix Plamper

Polymers 2018, 10(4), 429; https://doi.org/10.3390/polym10040429 - 12 Apr 2018

Cited by 7 | Viewed by 4977

Abstract

The effect of polyelectrolyte composition on the electrodeposition onto platinum is investigated using a counterion switching approach. Film formation of preformed polyelectrolytes is triggered by oxidation of hexacyanoferrates(II) (ferrocyanide), leading to polyelectrolyte complexes, which are physically crosslinked by hexacyanoferrate(III) (ferricyanide) ions due to [...] Read more.

The effect of polyelectrolyte composition on the electrodeposition onto platinum is investigated using a counterion switching approach. Film formation of preformed polyelectrolytes is triggered by oxidation of hexacyanoferrates(II) (ferrocyanide), leading to polyelectrolyte complexes, which are physically crosslinked by hexacyanoferrate(III) (ferricyanide) ions due to preferential ferricyanide/polycation interactions. In this study, the electrodeposition of three different linear polyelectrolytes, namely quaternized poly[2-(dimethylamino)ethyl methacrylate] (i.e., poly{[2-(methacryloyloxy)ethyl]trimethylammonium chloride}; PMOTAC), quaternized poly[2-(dimethylamino)ethyl acrylate] (i.e., poly{[2-(acryloyloxy)ethyl]trimethylammonium chloride}; POTAC), quaternized poly[N-(3-dimethylaminopropyl)methacrylamide] (i.e., poly{[3-(methacrylamido)propyl]trimethylammonium chloride}; PMAPTAC) and different statistical copolymers of these polyelectrolytes with N-(3-aminopropyl)methacrylamide (APMA), are studied. Hydrodynamic voltammetry utilizing a rotating ring disk electrode (RRDE) shows the highest deposition efficiency DE for PMOTAC over PMAPTAC and over POTAC. Increasing incorporation of APMA weakens the preferred interaction of the quaternized units with the hexacyanoferrate(III) ions. At a sufficient APMA content, electrodeposition can thus be prevented. Additional electrochemical quartz crystal microbalance measurements reveal the formation of rigid polyelectrolyte films being highly crosslinked by the hexacyanoferrate(III) ions. Results indicate a different degree of water incorporation into these polyelectrolyte films. Hence, by adjusting the polycation composition, film properties can be tuned, while different chemistries can be incorporated into these electrodeposited thin hydrogel films. Full article

(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)

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12 pages, 1632 KiB

Open AccessArticle

Effects of Different Temperatures on the Chemical Structure and Antitumor Activities of Polysaccharides from Cordyceps militaris

by Eliyas Nurmamat, Hongxing Xiao, Yan Zhang and Ziwei Jiao

Polymers 2018, 10(4), 430; https://doi.org/10.3390/polym10040430 - 12 Apr 2018

Cited by 37 | Viewed by 5390

Abstract

The effects of different extraction temperatures (4 and 80 °C) on the physicochemical properties and antitumor activity of water soluble polysaccharides (CMPs-4 and CMPs-80) from Cordyceps militaris (C. militaris) were evaluated in this study. The results of gas chromatography (GC) and high-performance gel [...] Read more.

The effects of different extraction temperatures (4 and 80 °C) on the physicochemical properties and antitumor activity of water soluble polysaccharides (CMPs-4 and CMPs-80) from Cordyceps militaris (C. militaris) were evaluated in this study. The results of gas chromatography (GC) and high-performance gel permeation chromatography (HPGPC) showed that a higher extraction temperature could degrade the polysaccharides with 188 kDa, mainly composed of glucose, and increase the dissolution rate of polysaccharides about 308 kDa, mainly consisting of rhamnose and galactose. In addition, the CMPs displayed the same sugar ring and category of glycosidic linkage based on Fourier-transform infrared spectroscopy (FTIR) analysis, however, their invisible structural difference occurred in the specific rotation and conformational characteristics according to the results of specific optical rotation measurement and Congo red test. In vitro antitumor experiments indicated that CMPs-4 possessed stronger inhibitory effects on human esophagus cancer Eca-109 cells by inducing cell apoptosis more than CMPs-80 did. These findings demonstrated that the polysaccharides extracted with cold water (4 °C) could be applied as a novel alternative chemotherapeutic agent or dietary supplement with its underlying antitumor property. Full article

(This article belongs to the Collection Polysaccharides)

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15 pages, 56235 KiB

Open AccessArticle

The Application of Small-Angle Light Scattering for Rheo-Optical Characterization of Chitosan Colloidal Solutions

by Piotr Owczarz, Patryk Ziółkowski and Marek Dziubiński

Polymers 2018, 10(4), 431; https://doi.org/10.3390/polym10040431 - 13 Apr 2018

Cited by 11 | Viewed by 6003

Abstract

In the recent studies on chitosan hydrogels, it was found that understanding both rheological and structural properties plays an important role in their application. Therefore, a combination of two independent techniques was applied to investigate micro- and macroscopic properties of chitosan colloidal system. [...] Read more.

In the recent studies on chitosan hydrogels, it was found that understanding both rheological and structural properties plays an important role in their application. Therefore, a combination of two independent techniques was applied to investigate micro- and macroscopic properties of chitosan colloidal system. Studies on viscous properties, as well as the sol-gel phase transition process, were performed using rheological methods coupled with the small angle light scattering (SALS) technique. Based on the anisotropy of scattering patterns obtained during rotational shear tests, it was found that the chitosan solution reveals two different behaviors delimited by the critical value of the shear rate. Below a critical value, chitosan clusters are deformed without breaking up aggregates, whereas after exceeding a critical value, chitosan clusters apart from deformation also breakup into smaller aggregates. The values of the radius of gyration determined by applying the Debye function allow one to state that with an increase of chitosan concentration, molecule size decreases. An analysis of the light scattering data from the temperature ramp test showed that with an increase of temperature, the level of polymer coil swelling increases. Simultaneously, the supply of thermal energy leads to a neutralization of the charge of chitosan chains. As a consequence, the formation of intermolecular links occurs and a gel structure is formed. Full article

(This article belongs to the Collection Polysaccharides)

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10 pages, 406 KiB

Open AccessArticle

Condensation of Counterions Gives Rise to Contraction Transitions in a One-Dimensional Polyelectrolyte Gel

by Gerald S. Manning

Polymers 2018, 10(4), 432; https://doi.org/10.3390/polym10040432 - 13 Apr 2018

Cited by 5 | Viewed by 3306

Abstract

The equilibrium volume of a polyelectrolyte gel results from a balance between the tendency to swell caused by outbound polymer/counterion diffusion along with Coulomb interactions on the one hand; and, on the other, the elastic resilience of the cross-linked polymer network. Direct Coulomb [...] Read more.

The equilibrium volume of a polyelectrolyte gel results from a balance between the tendency to swell caused by outbound polymer/counterion diffusion along with Coulomb interactions on the one hand; and, on the other, the elastic resilience of the cross-linked polymer network. Direct Coulomb forces contribute both to non-ideality of the equilibrated Donnan osmotic pressure, but also to stretching of the network. To isolate the effect of polyelectrolyte expansion, we have analyzed a “one-dimensional” version of a gel, a linear chain of charged beads connected by Hooke’s law springs. As in the range of weak Coulomb strengths previously studied, the springs are significantly stretched by the repulsive interactions among the beads even when the Coulomb strength is strong enough to cause condensation of counterions. There is a quasi-abrupt transition from a stretched state to a partially collapsed state in a transition range between weak and strong Coulomb strengths. Fluctuations between stretched and contracted conformations occur within the transition range. As the solvent quality decreases past the transition range, a progressive collapse can result if the condensed counterions strengthen the spring constant. Full article

(This article belongs to the Special Issue Ionic Polymers)

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15 pages, 36149 KiB

Open AccessArticle

Structural Changes of Bagasse dusring the Homogeneous Esterification with Maleic Anhydride in Ionic Liquid 1-Allyl-3-methylimidazolium Chloride

by Huihui Wang, Wei Chen, Xueqin Zhang, Yi Wei, Aiping Zhang, Shijie Liu, Xiaoying Wang and Chuanfu Liu

Polymers 2018, 10(4), 433; https://doi.org/10.3390/polym10040433 - 13 Apr 2018

Cited by 24 | Viewed by 4858

Abstract

The maleation of bagasse could greatly increase the compatibility between bagasse and composite matrixes, and the percentage of substitution (PS) of bagasse maleates could be regulated in the homogeneous system. However, due to the complicated components and the linkages of bagasse, it was [...] Read more.

The maleation of bagasse could greatly increase the compatibility between bagasse and composite matrixes, and the percentage of substitution (PS) of bagasse maleates could be regulated in the homogeneous system. However, due to the complicated components and the linkages of bagasse, it was difficult to control the reaction behaviors of each component. In this paper, the detailed structural changes of bagasse during the homogeneous maleation in ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) were comparatively investigated with the three main components (cellulose, hemicelluloses, and lignin) from bagasse. The PS of the maleated bagasse was 12.52%, and the PS of the maleated cellulose, hemicelluloses, and lignin were 13.50%, 10.89%, and 14.03%, respectively. Fourier translation infrared (FT-IR) and NMR analyses confirmed that the three main components were all involved in the homogeneous maleation. ¹H-¹³C HSQC analysis indicated that the predominant monoesterification of cellulose, diesterification of hemicelluloses and lignin, and the degradation of the three main components simultaneously occurred. Besides, the quantitative analysis from ¹H-¹³C HSQC revealed the relative PS of reactive sites in each component. ³¹P NMR results showed that the reactivity of lignin aliphatic hydroxyls was higher than that of phenolic ones, and the reactivity of phenolic hydroxyls followed the order of p-hydroxyphenyl hydroxyls > guaiacyl hydroxyls > syringyl hydroxyls. Full article

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17 pages, 8619 KiB

Open AccessArticle

Highly Efficient Luminescent Polycarboxylate Lanthanide Complexes Incorporated into Di-Ureasils by an In-Situ Sol—Gel Process

by Ming Fang, Lianshe Fu, Sandra F. H. Correia, Rute A. S. Ferreira and Luís D. Carlos

Polymers 2018, 10(4), 434; https://doi.org/10.3390/polym10040434 - 13 Apr 2018

Cited by 8 | Viewed by 4390

Abstract

In order to prepare efficient luminescent organic–inorganic hybrid materials embedded with a lanthanide (Ln³⁺) complex with polycarboxylate ligands, Ln³⁺-doped di-ureasils with 4,4-oxybis(benzoic acid) and 1,10-phenanthroline ligands were synthesized via an in-situ sol–gel route. The resulting hybrids were structurally, thermally, [...] Read more.

In order to prepare efficient luminescent organic–inorganic hybrid materials embedded with a lanthanide (Ln³⁺) complex with polycarboxylate ligands, Ln³⁺-doped di-ureasils with 4,4-oxybis(benzoic acid) and 1,10-phenanthroline ligands were synthesized via an in-situ sol–gel route. The resulting hybrids were structurally, thermally, and optically characterized. The energy levels of the ligands and the host-to-ion and ligand-to-ion energy transfer mechanisms were investigated (including DFT/TD–DFT calculations). The results show that these Ln³⁺-based di-ureasil hybrids exhibit promising luminescent features, e.g., Eu³⁺-based materials are bright red emitters displaying quantum yields up to 0.50 ± 0.05. The luminescent color can be fine-tuned either by selection of adequate Ln³⁺ ions or by variation of the excitation wavelength. Accordingly, white light emission with CIE coordinates of (0.33, 0.35) under 310 nm irradiation was obtained. Full article

(This article belongs to the Special Issue Polymeric Materials for Optical Applications)

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12 pages, 23020 KiB

Open AccessArticle

Synthesis and Characterization of Wooden Magnetic Activated Carbon Fibers with Hierarchical Pore Structures

by Dongna Li, Jianing Li, Biyun Ren, Tongtong Li and Xiaojun Ma

Polymers 2018, 10(4), 435; https://doi.org/10.3390/polym10040435 - 13 Apr 2018

Cited by 5 | Viewed by 4625

Abstract

Wooden magnetic activated carbon fibers (WMACFs) with hierarchical pore structures were obtained by adding magnetic iron oxide (Fe₃O₄) nanoparticles into the liquefied wood. The structures and properties of WMACFs were analyzed by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), Fourier [...] Read more.

Wooden magnetic activated carbon fibers (WMACFs) with hierarchical pore structures were obtained by adding magnetic iron oxide (Fe₃O₄) nanoparticles into the liquefied wood. The structures and properties of WMACFs were analyzed by scanning electronmicroscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N₂ adsorption, and vibrating sample magnetometer (VSM). The results showed that WMACFs had high Brunauer-Emmett-Teller (BET) surface area (1578 m²/g) and total pore volume (0.929 cm³/g), of which 45% was the contribution of small mesopores of 2–3 nm. It is believed that Fe₃O₄ nanoparticles play an important role in the formation of hierarchical pores. With the Fe₃O₄ content increasing, the yield rate of WMACFs decreased, and the Fe₃O₄ crystal plane diffraction peaks and characteristic adsorption peaks were obviously observed. At the same time, it was also found that WMACFs had favorable magnetic properties when the Fe₃O₄ content was above 1.5%. As a result, WMACFs could be a promising candidate for high efficiency, low cost, and convenient separation for the magnetic field. Full article

(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)

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12 pages, 3596 KiB

Open AccessArticle

Reinforced PEI/PVdF Multicore-Shell Structure Composite Membranes by Phase Prediction on a Ternary Solution

by Jihye Chae, Sejoon Park, Dong Young Kim, Han-Ik Joh, Jong Man Kim, Sungho Lee and Seong Mu Jo

Polymers 2018, 10(4), 436; https://doi.org/10.3390/polym10040436 - 13 Apr 2018

Cited by 3 | Viewed by 5332

Abstract

To construct a polyetherimide (PEI)-reinforced polyvinylidene fluoride (PVdF) composite membrane with multicore-shell structure, a ternary solution was prepared and electrospun by single-nozzle electrospinning. A theoretical prediction was made for the feasibility of complete distinction of two phases. The diameters of the membrane fibers [...] Read more.

To construct a polyetherimide (PEI)-reinforced polyvinylidene fluoride (PVdF) composite membrane with multicore-shell structure, a ternary solution was prepared and electrospun by single-nozzle electrospinning. A theoretical prediction was made for the feasibility of complete distinction of two phases. The diameters of the membrane fibers and the PEI multi-core fibrils varied with the PEI ratio and the spinning time, respectively. The tensile strength and modulus were improved to 48 MPa and 1.5 GPa, respectively. The shrinkage of the membrane was only 6.6% at 180 °C, at which temperature the commercial PE separator melted down. The reinforcement in mechanical and thermal properties is associated with multiple PEI nanofibrils oriented along the fiber axis. Indeed, the unique morphology of self-assembled multicore-shell fibers plays an important role in their properties. All in all, PEI/PVdF membranes are appropriate for a lithium-ion battery application due to their high mechanical strength, excellent thermal stability, and controllable textural properties. Full article

(This article belongs to the Special Issue Electrospinning of Nanofibres)

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14 pages, 17547 KiB

Open AccessArticle

Synthesis and Evaluation of 8-Aminoquinoline-Grafted Poly(glycidyl methacrylate) for the Recovery of Pd(II) from Highly Acidic Aqueous Solutions

by Bing Zhang, Shixing Wang, Likang Fu and Libo Zhang

Polymers 2018, 10(4), 437; https://doi.org/10.3390/polym10040437 - 14 Apr 2018

Cited by 22 | Viewed by 4775

Abstract

A new adsorbent was prepared via modified poly(glycidyl methacrylate) with 8-aminoquinoline (AQ-PGMA) for the recovery of Pd(II) from solution. The practical application values of AQ-PGMA, including efficiency, selectivity and reusability for the recovery of Pd(II), are proved by the various experiment parameters. The [...] Read more.

A new adsorbent was prepared via modified poly(glycidyl methacrylate) with 8-aminoquinoline (AQ-PGMA) for the recovery of Pd(II) from solution. The practical application values of AQ-PGMA, including efficiency, selectivity and reusability for the recovery of Pd(II), are proved by the various experiment parameters. The parameters include HCl concentration, adsorption time, initial Pd(II) concentration, coexisting ions and reused cycles. The prepared AQ-PGMA showed a high adsorbing capacity for Pd(II) (up to 267.90 mg/g) when the concentration of HCl is higher than 0.4 mol/L. The analysis of the adsorption process indicated that the adsorption kinetics followed a pseudo-second-order kinetic model and the adsorption isotherms obeyed the Hill model. The Hill model showed that one adsorption site on the AQ-PGMA could combine 1.45 Pd(II). In addition, the obtained adsorbent demonstrated good regenerative ability and satisfying selectivity for the recovery of Pd(II). The adsorption mechanism was dominated by the chelation and ion exchange reactions between amines/hydroxyl groups and Pd(II). The experiments confirmed that AQ-PGMA was efficient for recovery of Pd(II) from highly acidic aqueous solutions. Full article

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10 pages, 20156 KiB

Open AccessArticle

Study on the Use of Microbial Cellulose as a Biocarrier for 1,3-Dihydroxy-2-Propanone and Its Potential Application in Industry

by Lidia Stasiak-Różańska and Justyna Płoska

Polymers 2018, 10(4), 438; https://doi.org/10.3390/polym10040438 - 14 Apr 2018

Cited by 26 | Viewed by 6502

Abstract

Can microbial cellulose (MC) be used as a bio-carrier for 1,3-dihydroxy-2-propanone (DHA)? The aim of this study was to examine the possibility of using MC as a biomaterial for DHA transferring into the stratum corneum and inducing changes in skin color. The MC [...] Read more.

Can microbial cellulose (MC) be used as a bio-carrier for 1,3-dihydroxy-2-propanone (DHA)? The aim of this study was to examine the possibility of using MC as a biomaterial for DHA transferring into the stratum corneum and inducing changes in skin color. The MC patches were obtained from Gluconacetobacter xylinus strain and incubated in solutions with various concentrations of DHA (g·L⁻¹: 20; 50; 80; 110) at 22 °C for 24 h. Afterwards; the patches were applied onto the skin for 15, 30, or 60 min. Skin color changes were assessed visually compared to a control patches without DHA. The intensity of skin color was increasing with the increase of DHA concentration and time of patches application. Application of MC patches with DHA (50 g·L⁻¹) for 30 min ensured the color which was considered the closest to the desired natural tan effect. MC patches containing DHA can be biocarriers enabling DHA transport into the stratum corneum and causing skin color changes. Study results indicate a new possibility for industrial applications of MC; e.g., as a biocarrier in masking the symptoms of vitiligo or production of self-tanning agents in the form of masks. Full article

(This article belongs to the Special Issue Polysaccharides)

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13 pages, 4822 KiB

Open AccessArticle

Effect of Selected Thiols on Cross-Linking of Acrylated Epoxidized Soybean Oil and Properties of Resulting Polymers

by Sigita Kasetaite, Silvia De la Flor, Angels Serra and Jolita Ostrauskaite

Polymers 2018, 10(4), 439; https://doi.org/10.3390/polym10040439 - 14 Apr 2018

Cited by 22 | Viewed by 9989

Abstract

The effect of the chemical structure and functionality of three structurally different thiols on the cross-linking of acrylated epoxidized soybean oil and on the properties of the resulting polymers was investigated in this study. 1,3-Benzenedithiol, pentaerythritol tetra(3-mercaptopropionate), and an hexathiol synthesized from squalene [...] Read more.

The effect of the chemical structure and functionality of three structurally different thiols on the cross-linking of acrylated epoxidized soybean oil and on the properties of the resulting polymers was investigated in this study. 1,3-Benzenedithiol, pentaerythritol tetra(3-mercaptopropionate), and an hexathiol synthesized from squalene were used in the cross-linking of acrylated epoxidized soybean oil by thiol–Michael addition reaction. The reactivity of thiols determined from calorimetric curves followed the order: 1,3-benzenedithiol > pentaerythritol tetra(3-mercaptopropionate) > hexathiolated squalene. Thermal and mechanical properties and the swelling in different solvents of the cross-linked polymers were studied. The cross-linked polymer obtained from 1,3-benzenedithiol showed the highest swelling values in chloroform and toluene. The cross-linked polymer with pentaerythritol tetra(3-mercaptopropionate) fragments showed the best mechanical performance (highest mechanical strength and Young’s modulus) and thermal stability. The cross-linked polymers from hexathiolated squalene showed the highest glass transition temperature. Full article

(This article belongs to the Special Issue Bio-Based Resins and Crosslinked Polymers from Renewable Resources)

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16 pages, 5779 KiB

Open AccessArticle

Towards More Sustainable Material Formulations: A Comparative Assessment of PA11-SGW Flexural Performance versus Oil-Based Composites

by Helena Oliver-Ortega, José Alberto Méndez, Rafel Reixach, Francesc Xavier Espinach, Mònica Ardanuy and Pere Mutjé

Polymers 2018, 10(4), 440; https://doi.org/10.3390/polym10040440 - 14 Apr 2018

Cited by 21 | Viewed by 5319

Abstract

The replacement of commodity polyolefin, reinforced with glass fiber (GF), by greener alternatives has been a topic of research in recent years. Cellulose fibers have shown, under certain conditions, enough tensile capacities to replace GF, achieving competitive mechanical properties. However, if the objective [...] Read more.

The replacement of commodity polyolefin, reinforced with glass fiber (GF), by greener alternatives has been a topic of research in recent years. Cellulose fibers have shown, under certain conditions, enough tensile capacities to replace GF, achieving competitive mechanical properties. However, if the objective is the production of environmentally friendlier composites, it is necessary to replace oil-derived polymer matrices by bio-based or biodegradable ones, depending on the application. Polyamide 11 (PA11) is a totally bio-based polyamide that can be reinforced with cellulosic fibers. Composites based on this polymer have demonstrated enough tensile strength, as well as stiffness, to replace GF-reinforced polypropylene (PP). However, flexural properties are of high interest for engineering applications. Due to the specific character of short-fiber-reinforced composites, significant differences are expected between the tensile and flexural properties. These differences encourage the study of the flexural properties of a material prior to the design or development of a new product. Despite the importance of the flexural strength, there are few works devoted to its study in the case of PA11-based composites. In this work, an in-depth study of the flexural strength of PA11 composites, reinforced with Stoneground wood (SGW) from softwood, is presented. Additionally, the results are compared with those of PP-based composites. The results showed that the SGW fibers had lower strengthening capacity reinforcing PA11 than PP. Moreover, the flexural strength of PA11-SGW composites was similar to that of PP-GF composites. Full article

(This article belongs to the Collection Polymeric Adhesives)

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14 pages, 14702 KiB

Open AccessArticle

Synthesis of an Efficient S/N-Based Flame Retardant and Its Application in Polycarbonate

by Weiqiu Wen, Jianwei Guo, Xi Zhao, Xiong Li, Hongmei Yang and Jem-Kun Chen

Polymers 2018, 10(4), 441; https://doi.org/10.3390/polym10040441 - 14 Apr 2018

Cited by 12 | Viewed by 4834

Abstract

Considering the poor compatibility and water-resistance of sulfonate flame retardants for polycarbonate (PC), an efficient S/N-based flame retardant named 1,3,5,7-tetrakis(phenyl-4-sulfonyl-melamine)adamantane (ASN) has been developed. Fire properties studies of PC/ASN blends indicate that the addition of 0.10 wt % ASN imparts a V-0 rating [...] Read more.

Considering the poor compatibility and water-resistance of sulfonate flame retardants for polycarbonate (PC), an efficient S/N-based flame retardant named 1,3,5,7-tetrakis(phenyl-4-sulfonyl-melamine)adamantane (ASN) has been developed. Fire properties studies of PC/ASN blends indicate that the addition of 0.10 wt % ASN imparts a V-0 rating and a limited oxygen index (LOI) value of 30.1% to PC specimens, and ASN can suppress the heat and toxic gas release of PC composites. Additionally, PC/ASN blends are believed to be exceptional materials for outdoor PC applications due to their superior water-resistance properties. Moreover, mechanical properties were further systematically investigated, and the correlative results indicate that the tensile strength and rigidity of specimens are improved with the addition of ASN. Full article

(This article belongs to the Special Issue Core-Shell Structured Polymers)

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15 pages, 3525 KiB

Open AccessArticle

Comparative Study of Diethylaminoethyl-Chitosan and Methylglycol-Chitosan as Potential Non-Viral Vectors for Gene Therapy

by Sergei V. Raik, Stanislav Andranovitš, Valentina A. Petrova, Yingying Xu, Jenny Ka-Wing Lam, Gordon A. Morris, Alexandra V. Brodskaia, Luca Casettari, Andreii S. Kritchenkov and Yury A. Skorik

Polymers 2018, 10(4), 442; https://doi.org/10.3390/polym10040442 - 14 Apr 2018

Cited by 42 | Viewed by 6572

Abstract

In this paper, we compared the transfection efficiency and cytotoxicity of methylglycol-chitosan (MG-CS) and diethylaminoethyl-chitosan (DEAE-CS_I and DEAE-CS_II with degrees of substitution of 1.2 and 0.57, respectively) to that of Lipofectamine (used as a reference transfection vector). MG-CS contains quaternary amines [...] Read more.

In this paper, we compared the transfection efficiency and cytotoxicity of methylglycol-chitosan (MG-CS) and diethylaminoethyl-chitosan (DEAE-CS_I and DEAE-CS_II with degrees of substitution of 1.2 and 0.57, respectively) to that of Lipofectamine (used as a reference transfection vector). MG-CS contains quaternary amines to improve DNA binding, whereas the DEAE-CS exhibits pH buffering capability that would ostensibly enhance transfection efficiency by promoting endosomal escape. Gel retardation assays showed that both DEAE-CS and MG-CS bound to DNA at a polysaccharide:DNA mass ratio of 2:1. In Calu-3 cells, the DNA transfection activity was significantly better with MG-CS than with DEAE-CS, and the efficiency improved with increasing polysaccharide:DNA ratios. By contrast, the efficiency of DEAE-CS_I and DEAE-CS_II was independent of the polysaccharide:DNA ratio. Conversely, in the transfection-recalcitrant JAWSII cells, both Lipofectamine and MG-CS showed significantly lower DNA transfection activity than in Calu-3 cells, whereas the efficiency of DEAE-CS_I and DEAE-CS_II was similar in both cell lines. The toxicity of DEAE-CS increased with increasing concentrations of the polymer and its degree of substitution, whereas MG-CS demonstrated negligible cytotoxicity, even at the highest concentration studied. Overall, MG-CS proved to be a more efficient and less toxic transfection agent when compared to DEAE-CS. Full article

(This article belongs to the Collection Polysaccharides)

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15 pages, 26414 KiB

Open AccessArticle

pH-Sensitive Micelles Based on Star Copolymer Ad-(PCL-b-PDEAEMA-b-PPEGMA)₄ for Controlled Drug Delivery

by Huiyan Yang, Jianwei Guo, Rui Tong, Chufen Yang and Jem-Kun Chen

Polymers 2018, 10(4), 443; https://doi.org/10.3390/polym10040443 - 14 Apr 2018

Cited by 17 | Viewed by 5284

Abstract

Enhancing drug loading efficacy and stability of polymeric micelles remains a grand challenge. Here we develop adamantane-based star copolymers adamantane-[poly(ε-caprolactone)-b-poly(2-(diethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate)]₄ (Ad-(PCL-b-PDEAEMA-b-PPEGMA)₄) and their self-assembled micelles for controlled [...] Read more.

Enhancing drug loading efficacy and stability of polymeric micelles remains a grand challenge. Here we develop adamantane-based star copolymers adamantane-[poly(ε-caprolactone)-b-poly(2-(diethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate)]₄ (Ad-(PCL-b-PDEAEMA-b-PPEGMA)₄) and their self-assembled micelles for controlled drug delivery. Results show that the polymers have excellent stability in solution with low critical micelle concentration (CMC) (0.0025–0.0034 mg/mL) and the apparent base dissociation constant (pK_b) of the polymers is from 5.31 to 6.05. Dynamic light scattering analysis exhibits the great environmental response capability of the pH-sensitive micelles according to particle sizes and zeta potentials. With the synergy effect of the adamantane and hydrophobic block, the micelles display the high Doxorubicin (DOX) loading efficacy (up to 22.4%). The DOX release study shows that the micelles are capable of controlled release for drug. This work indicates the Ad-(PCL-b-PDEAEMA-b-PPEGMA)₄ micelles may provide new guidelines for drug control and release system in overcoming cancer treatment. Full article

(This article belongs to the Special Issue Core-Shell Structured Polymers)

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12 pages, 5824 KiB

Open AccessArticle

Non-Leachable Hydrophilic Additives for Amphiphilic Coatings

by Guillaume Gillet, Fabrice Azemar, Fabienne Faÿ, Karine Réhel and Isabelle Linossier

Polymers 2018, 10(4), 445; https://doi.org/10.3390/polym10040445 - 16 Apr 2018

Cited by 6 | Viewed by 5774

Abstract

Amphiphilic surfaces are particularly effective at inhibiting the adhesion of microorganisms (bacteria, cells, microalgae, etc.) in liquid media. The aim of this study is to determine the best hydrophilic linker to promote bonding between poly(ethylene glycol) (PEG) as a hydrophilic additive and poly(dimethyl [...] Read more.

Amphiphilic surfaces are particularly effective at inhibiting the adhesion of microorganisms (bacteria, cells, microalgae, etc.) in liquid media. The aim of this study is to determine the best hydrophilic linker to promote bonding between poly(ethylene glycol) (PEG) as a hydrophilic additive and poly(dimethyl siloxane) (PDMS) as the hydrophobic matrix. Various parameters have been studied (molecular weight, linker type, and polymer end-group), as well as the efficiency of the linking, the capacity of PEG to access to the surface of the film, and overall film homogeneity. According to the results, a PDMS linker paired with a PEG moiety allows for compatibilization of the compounds during cross-linking. This compatibilization seems to provide a good bonding with the matrix and a good surface access to the hydrophilic moiety. Therefore, this structure comprising a linking function attached to the PDMS–PEG copolymer has high potential as a non-releasable additive for amphiphilic coating applications. Full article

(This article belongs to the Special Issue Siloxane-Based Polymers)

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15 pages, 4785 KiB

Open AccessArticle

Modelling Filler Dispersion in Elastomers: Relating Filler Morphology to Interface Free Energies via SAXS and TEM Simulation Studies

by Norman Gundlach and Reinhard Hentschke

Polymers 2018, 10(4), 446; https://doi.org/10.3390/polym10040446 - 16 Apr 2018

Cited by 23 | Viewed by 8299

Abstract

The properties of rubber are strongly influenced by the distribution of filler within the polymer matrix. Here, we introduce a Monte Carlo-based morphology generator. The basic elements of our model are cubic cells, which, in the current version, can be either silica filler [...] Read more.

The properties of rubber are strongly influenced by the distribution of filler within the polymer matrix. Here, we introduce a Monte Carlo-based morphology generator. The basic elements of our model are cubic cells, which, in the current version, can be either silica filler particles or rubber volume elements in adjustable proportion. The model allows the assignment of surface free energies to the particles according to whether a surface represents, for instance, ‘naked’ silica or silanised silica. The amount of silanisation is variable. We use a nearest-neighbour site-exchange Monte Carlo algorithm to generate filler morphologies, mimicking flocculation. Transmission electron micrographs (TEM) as well as small angle scattering (SAS) intensities can be calculated along the Monte Carlo trajectory. In this work, we demonstrate the application of our morphology generator in terms of selected examples. We illustrate its potential as a tool for screening studies, relating interface tensions between the components to filler network structure as characterised by TEM and SAS. Full article

(This article belongs to the Special Issue Elastomers)

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14 pages, 901 KiB

Open AccessArticle

An Accurate Estimate of the Free Energy and Phase Diagram of All-DNA Bulk Fluids

by Emanuele Locatelli and Lorenzo Rovigatti

Polymers 2018, 10(4), 447; https://doi.org/10.3390/polym10040447 - 16 Apr 2018

Cited by 5 | Viewed by 4386

Abstract

We present a numerical study in which large-scale bulk simulations of self-assembled DNA constructs have been carried out with a realistic coarse-grained model. The investigation aims at obtaining a precise, albeit numerically demanding, estimate of the free energy for such systems. We then, [...] Read more.

We present a numerical study in which large-scale bulk simulations of self-assembled DNA constructs have been carried out with a realistic coarse-grained model. The investigation aims at obtaining a precise, albeit numerically demanding, estimate of the free energy for such systems. We then, in turn, use these accurate results to validate a recently proposed theoretical approach that builds on a liquid-state theory, the Wertheim theory, to compute the phase diagram of all-DNA fluids. This hybrid theoretical/numerical approach, based on the lowest-order virial expansion and on a nearest-neighbor DNA model, can provide, in an undemanding way, a parameter-free thermodynamic description of DNA associating fluids that is in semi-quantitative agreement with experiments. We show that the predictions of the scheme are as accurate as those obtained with more sophisticated methods. We also demonstrate the flexibility of the approach by incorporating non-trivial additional contributions that go beyond the nearest-neighbor model to compute the DNA hybridization free energy. Full article

(This article belongs to the Special Issue Selected Papers from "ECIS 2017")

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12 pages, 26061 KiB

Open AccessArticle

Antifungal Paper Based on a Polyborneolacrylate Coating

by Jiangqi Xu, Yujia Bai, Meijiao Wan, Yanhui Liu, Lei Tao and Xing Wang

Polymers 2018, 10(4), 448; https://doi.org/10.3390/polym10040448 - 17 Apr 2018

Cited by 15 | Viewed by 5331

Abstract

Paper documents and products are very susceptible to microbial contamination and damage. Fungi are mainly responsible for those biodeterioration processes. Traditional microbicidal strategies constitute a serious health risk even when microbes are dead. Ideal methods should not be toxic to humans and should [...] Read more.

Paper documents and products are very susceptible to microbial contamination and damage. Fungi are mainly responsible for those biodeterioration processes. Traditional microbicidal strategies constitute a serious health risk even when microbes are dead. Ideal methods should not be toxic to humans and should have no adverse effects on paper, but should own a broad spectrum, good chemical stability and low cost. In this work, we utilize an advanced antimicrobial strategy of surface stereochemistry by applying a coating of a shallow layer of polyborneolacrylate (PBA), resulting in the desired antifungal performance. The PBA-coated paper is challenged with the most common air-borne fungi growing on paper, Aspergillus niger and Penicillium sp. Ten percent by weight of the coating concentration or a 19-μm infiltration of PBA is sufficient to keep the paper spotless. The PBA coating also exhibits significant inhibition of spores’ germination. After PBA coating, both physicochemical properties (paper whiteness, pH, mechanical strength) and inking performance display only slight changes, which are acceptable for general utilization. This PBA coating method is nontoxic, rapid and cost-effective, thus demonstrating great potential for applications in paper products. Full article

(This article belongs to the Special Issue Antimicrobial Polymers)

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12 pages, 2107 KiB

Open AccessArticle

High-Performance and Simply-Synthesized Ladder-Like Structured Methacrylate Siloxane Hybrid Material for Flexible Hard Coating

by Yun Hyeok Kim, Gwang-Mun Choi, Jin Gyu Bae, Yong Ho Kim and Byeong-Soo Bae

Polymers 2018, 10(4), 449; https://doi.org/10.3390/polym10040449 - 17 Apr 2018

Cited by 35 | Viewed by 10250

Abstract

A high performance ladder-like structured methacrylate siloxane hybrid material (LMSH) was fabricated via simple hydrolytic sol–gel reaction, followed by free-radical polymerization. A structurally ordered siloxane backbone, the ladder-like structure, which is an essential factor for high performance, could be achieved by a short [...] Read more.

A high performance ladder-like structured methacrylate siloxane hybrid material (LMSH) was fabricated via simple hydrolytic sol–gel reaction, followed by free-radical polymerization. A structurally ordered siloxane backbone, the ladder-like structure, which is an essential factor for high performance, could be achieved by a short period of sol–gel reaction in only 4 h. This results in superior optical (Transmittance > 90% at 550 nm), thermal (T_{5 wt % decomposition} > 400

℃

), mechanical properties(elastic recovery = 0.86, hardness = 0.6 GPa) compared to the random- and even commercialized cage-structured silsesquioxane, which also has ordered structure. It was investigated that the fabricated ladder-like structured MSH showed the highest overall density of organic/inorganic co-networks that are originated from highly ordered siloxane network, along with high conversion rate of polymerizable methacrylate groups. Our findings suggest a potential of the ladder-like structured MSH as a powerful alternative for the methacrylate polysilsesquioxane, which can be applied to thermally stable and flexible optical coatings, even with an easier and simpler preparation process. Full article

(This article belongs to the Collection Silicon-Containing Polymeric Materials)

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19 pages, 9074 KiB

Open AccessArticle

Soluble Electrochromic Polymers Incorporating Benzoselenadiazole and Electron Donor Units (Carbazole or Fluorene): Synthesis and Electronic-Optical Properties

by Jianzhong Xu, Qi Ji, Lingqian Kong, Hongmei Du, Xiuping Ju and Jinsheng Zhao

Polymers 2018, 10(4), 450; https://doi.org/10.3390/polym10040450 - 17 Apr 2018

Cited by 26 | Viewed by 4016

Abstract

A series of π-conjugated polymers containing alternating benzoselenadiazole (BSe)-bi(thiophene derivative)-carbazole or benzoththiadiazole (BSe)-bi(thiophene derivative)-fluorene units were designed and synthesized. Thiophene derivatives, namely 3-hexylthiophene, 3,4-bihexyloxythiophene, and 3,4-bioctyloxythiophene, were used as the π-bridges of the polymers. The polymers were characterized in detail in terms of [...] Read more.

A series of π-conjugated polymers containing alternating benzoselenadiazole (BSe)-bi(thiophene derivative)-carbazole or benzoththiadiazole (BSe)-bi(thiophene derivative)-fluorene units were designed and synthesized. Thiophene derivatives, namely 3-hexylthiophene, 3,4-bihexyloxythiophene, and 3,4-bioctyloxythiophene, were used as the π-bridges of the polymers. The polymers were characterized in detail in terms of their thermal stabilities, cyclic voltammograms, UV-Vis absorption, spectroelectrochemistry, dynamic switching property and so forth. The alkoxy thiophene π-bridged polymers have lower onset oxidation potentials and bandgaps than that of their corresponding alkyl thiophene π-bridged polymers. The selection of the donor units between the carbazole and the fluorene units has nearly no effect on the bandgaps and colors as well as the onset oxidation potentials of the polymers. The increase in the length of the side alkyl chains on the thiophene ring caused a slight increase in the polymer bandgap, which may be caused by the space hindrance effect. The dynamic switching abilities of the polymers were obtained by the chronoabsorptometry method, and the results also suggested that the alkoxy thiophene-containing polymers (as π-bridges) have higher contrast ratios than the corresponding alkyl thiophene-containing polymers. Furthermore, the increase in the length of the side alkyl chain might have a detrimental effect on the optical contrast ratios of the polymers. Full article

(This article belongs to the Special Issue Electrochromic Polymers)

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23 pages, 4141 KiB

Open AccessArticle

The Role of Chain Molecular Weight and Hofmeister Series Ions in Thermal Aggregation of Poly(2-Isopropyl-2-Oxazoline) Grafted Nanoparticles

by Martina Schroffenegger, Ronald Zirbs, Steffen Kurzhals and Erik Reimhult

Polymers 2018, 10(4), 451; https://doi.org/10.3390/polym10040451 - 17 Apr 2018

Cited by 18 | Viewed by 4997

Abstract

Thermoresponsive nanoparticles are promising smart materials for many applications. However, a rational design for applications requires a deeper understanding and experimental verification of the various parameters that influence the thermoresponsiveness of the spherical polymer brushes that define most of such nanomaterials. Therefore, we [...] Read more.

Thermoresponsive nanoparticles are promising smart materials for many applications. However, a rational design for applications requires a deeper understanding and experimental verification of the various parameters that influence the thermoresponsiveness of the spherical polymer brushes that define most of such nanomaterials. Therefore, we investigate superparamagnetic iron oxide nanoparticles (SPION) grafted with poly(2-isopropyl-2-oxazoline) (6–33 kg mol⁻¹) by temperature-cycled dynamic light scattering and differential scanning calorimetry. The grafting of dense spherical polymer brushes leads to lower aggregation temperatures and transition enthalpies when compared with the free polymer. The transition enthalpy and temperature depend on the polymer shell size and structure. The addition of kosmotropic salts decreases the aggregation temperature following the Hofmeister series. Full article

(This article belongs to the Special Issue Stimuli Responsive Polymers)

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19 pages, 3389 KiB

Open AccessArticle

Biocompatible and Antibacterial Nitric Oxide-Releasing Pluronic F-127/Chitosan Hydrogel for Topical Applications

by Milena T. Pelegrino, Bruna De Araujo Lima, Mônica H. M. Do Nascimento, Christiane B. Lombello, Marcelo Brocchi and Amedea B. Seabra

Polymers 2018, 10(4), 452; https://doi.org/10.3390/polym10040452 - 18 Apr 2018

Cited by 65 | Viewed by 9159

Abstract

Nitric oxide (NO) is involved in physiological processes, including vasodilatation, wound healing and antibacterial activities. As NO is a free radical, designing drugs to generate therapeutic amounts of NO in controlled spatial and time manners is still a challenge. In this study, the [...] Read more.

Nitric oxide (NO) is involved in physiological processes, including vasodilatation, wound healing and antibacterial activities. As NO is a free radical, designing drugs to generate therapeutic amounts of NO in controlled spatial and time manners is still a challenge. In this study, the NO donor S-nitrosoglutathione (GSNO) was incorporated into the thermoresponsive Pluronic F-127 (PL)-chitosan (CS) hydrogel, with an easy and economically feasible methodology. CS is a polysaccharide with known antimicrobial properties. Scanning electron microscopy, rheology and differential scanning calorimetry techniques were used for hydrogel characterization. The results demonstrated that the hydrogel has a smooth surface, thermoresponsive behavior and good mechanical stability. The kinetics of NO release and GSNO diffusion from GSNO-containing PL/CS hydrogel demonstrated a sustained NO/GSNO release, in concentrations suitable for biomedical applications. The GSNO-PL/CS hydrogel demonstrated a concentration-dependent toxicity to Vero cells, and antimicrobial activity to Pseudomonas aeruginosa (minimum inhibitory concentration and minimum bactericidal concentration values of 0.5 µg·mL⁻¹ of hydrogel, which corresponds to 1 mmol·L⁻¹ of GSNO). Interestingly, the concentration range in which the NO-releasing hydrogel demonstrated an antibacterial effect was not found to be toxic to the Vero mammalian cell. Thus, the GSNO-PL/CS hydrogel is a suitable biomaterial for topical NO delivery applications. Full article

(This article belongs to the Collection Polysaccharides)

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10 pages, 2804 KiB

Open AccessArticle

Angular Photochromic LC Composite Film for an Anti-Counterfeiting Label

by Yanzi Gao, Wenhuan Yao, Jian Sun, Kexuan Li and Lanying Zhang

Polymers 2018, 10(4), 453; https://doi.org/10.3390/polym10040453 - 18 Apr 2018

Cited by 18 | Viewed by 4147

Abstract

In the harsh application environment, improving the mechanical properties of liquid crystal materials is a fundamental and important problem in the design of anti-counterfeit materials. In this paper, by a stepwise polymerization of first, photo-polymerization and subsequently thermal-polymerization, a coexistent polymer dispersed network [...] Read more.

In the harsh application environment, improving the mechanical properties of liquid crystal materials is a fundamental and important problem in the design of anti-counterfeit materials. In this paper, by a stepwise polymerization of first, photo-polymerization and subsequently thermal-polymerization, a coexistent polymer dispersed network was first constructed in cholesteric liquid crystal materials containing a photo-polymerizable system of urethane acrylate and a thermo-polymerizable system of isocyanate. Results revealed that the coexistent polymer dispersed network exhibited largely enhanced mechanical performance, and the networks obtained by different methods had different contributions to the enhancement of the peel strength and toughness of the composite films. Then an angular photochromic anti-fake label based on a coexistent polymer dispersed network with enhanced mechanical and apparent angular discoloration characteristics, suitable for practical applications, was successfully achieved. Full article

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13 pages, 2474 KiB

Open AccessArticle

Thermal Dependence of Optical Parameters of Thin Polythiophene Films Blended with PCBM

by Janusz Jaglarz, Anna Małek and Jerzy Sanetra

Polymers 2018, 10(4), 454; https://doi.org/10.3390/polym10040454 - 19 Apr 2018

Cited by 9 | Viewed by 4126

Abstract

The main purpose of this work is to show the thermal dependence of the refractive and extinction indices of conjugated polymer films used in optoelectronics devices. Herein, we present the results of optical investigations performed for the following polymers: poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT), [...] Read more.

The main purpose of this work is to show the thermal dependence of the refractive and extinction indices of conjugated polymer films used in optoelectronics devices. Herein, we present the results of optical investigations performed for the following polymers: poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT), and their blends with [6,6]-phenyl C61 butyric acid methyl ester (PCBM). For our analysis, we chose well-known polythiophenes such P3HT and P3OT, often used in photovoltaic cells. Our addition of PCMB to the polythiophenes allows their conversion efficiency to be increased. This paper presents the results of our investigation determining the spectral dispersion of optical constants in a wavelength range of 190–1700 nm by using spectroscopic ellipsometry (SE). Furthermore, we show the temperature dependence of the refractive indices of polythiophene films for a heating and a cooling process in the temperature range 25–130 °C. Additionally, thermo-optic coefficients and an optical gap were established and are presented in the paper, followed by a discussion on the conditions of the thermal stability of polythiophene blends and reversibility issues in thermal processes. Our paper presents a new and fresh analysis of depolarization beams after their reflection from the studied films. The paper presents the results of thermo-optical studies of polymer blends which have not been included in previously published works. Full article

(This article belongs to the Special Issue Polymeric Materials for Optical Applications)

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18 pages, 3400 KiB

Open AccessArticle

New Three-Dimensional Poly(decanediol-co-tricarballylate) Elastomeric Fibrous Mesh Fabricated by Photoreactive Electrospinning for Cardiac Tissue Engineering Applications

by Hesham M. Ismail, Somayeh Zamani, Mohamed A. Elrayess, Wael Kafienah and Husam M. Younes

Polymers 2018, 10(4), 455; https://doi.org/10.3390/polym10040455 - 19 Apr 2018

Cited by 19 | Viewed by 5110

Abstract

Reactive electrospinning is capable of efficiently producing in situ crosslinked scaffolds resembling the natural extracellular matrix with tunable characteristics. In this study, we aimed to synthesize, characterize, and investigate the in vitro cytocompatibility of electrospun fibers of acrylated poly(1,10-decanediol-co-tricarballylate) copolymer prepared [...] Read more.

Reactive electrospinning is capable of efficiently producing in situ crosslinked scaffolds resembling the natural extracellular matrix with tunable characteristics. In this study, we aimed to synthesize, characterize, and investigate the in vitro cytocompatibility of electrospun fibers of acrylated poly(1,10-decanediol-co-tricarballylate) copolymer prepared utilizing the photoreactive electrospinning process with ultraviolet radiation for crosslinking, to be used for cardiac tissue engineering applications. Chemical, thermal, and morphological characterization confirmed the successful synthesis of the polymer used for production of the electrospun fibrous scaffolds with more than 70% porosity. Mechanical testing confirmed the elastomeric nature of the fibers required to withstand cardiac contraction and relaxation. The cell viability assay showed no significant cytotoxicity of the fibers on cultured cardiomyoblasts and the cell-scaffolds interaction study showed a significant increase in cell attachment and growth on the electrospun fibers compared to the reference. This data suggests that the newly synthesized fibrous scaffold constitutes a promising candidate for cardiac tissue engineering applications. Full article

(This article belongs to the Special Issue Elastomers)

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16 pages, 4425 KiB

Open AccessArticle

Collagen/Gelatin/Hydroxyethyl Cellulose Composites Containing Microspheres Based on Collagen and Gelatin: Design and Evaluation

by Justyna Kozlowska, Natalia Stachowiak and Alina Sionkowska

Polymers 2018, 10(4), 456; https://doi.org/10.3390/polym10040456 - 19 Apr 2018

Cited by 35 | Viewed by 8463

Abstract

The objective of this study was to develop three-dimensional collagen/gelatin/hydroxyethyl cellulose composites in combination with gelatin or collagen-gelatin loaded microspheres. Microspheres were prepared by an emulsification/crosslinking method. A 1-Ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mixture were used as a [...] Read more.

The objective of this study was to develop three-dimensional collagen/gelatin/hydroxyethyl cellulose composites in combination with gelatin or collagen-gelatin loaded microspheres. Microspheres were prepared by an emulsification/crosslinking method. A 1-Ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) mixture were used as a crosslinking agent for the obtained materials. The structure of the materials was studied using scanning electron microscopy (SEM) and infrared spectroscopy. Moreover, a Calendula officinalis (pot marigold) flower extract release profile of the microsphere-loaded matrices was assessed in vitro. Additionally, porosity, density, stability, swelling and mechanical properties were tested. On the basis of SEM images, the microspheres exhibited a spherical shape and were irregularly dispersed in the polymer matrix. However, it was found that the addition of microparticles to obtained materials did not significantly change their microstructure. We observed a slight decrease in the swelling properties of matrices and an increase in values of Young’s modulus. Significantly, the addition of microspheres to the polymer matrices led to improved loading capacity of materials and release performance of Calendula officinalis flower extract. This makes the collagen/gelatin/hydroxyethyl cellulose composites containing microspheres a promising and suitable vehicle for biomedical, dermatological, or cosmetic applications. Full article

(This article belongs to the Collection Polysaccharides)

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11 pages, 4724 KiB

Open AccessArticle

Thermal Conductivity of Aluminosilicate- and Aluminum Oxide-Filled Thermosets for Injection Molding: Effect of Filler Content, Filler Size and Filler Geometry

by Yang Zhao, Zhanyu Zhai and Dietmar Drummer

Polymers 2018, 10(4), 457; https://doi.org/10.3390/polym10040457 - 20 Apr 2018

Cited by 21 | Viewed by 8976

Abstract

In this study, epoxy molding compounds (EMCs) with aluminosilicate (AlS) and aluminum oxide (AlO) were fabricated as fillers by a twin-screw-extruder (TSE) and shaped to plate samples using injection molding. AlS and AlO, electrical insulating mineral materials, were used as fillers to improve [...] Read more.

In this study, epoxy molding compounds (EMCs) with aluminosilicate (AlS) and aluminum oxide (AlO) were fabricated as fillers by a twin-screw-extruder (TSE) and shaped to plate samples using injection molding. AlS and AlO, electrical insulating mineral materials, were used as fillers to improve the thermal conductivity (λ_c) of composites. Composites with different filler particle sizes, filler contents and filler geometry were fabricated and the influence of these variables on the λ_c was studied. The λ_c of composites was measured with the hot-disk method. The distribution of fillers in composites was observed using scanning electron microscopy (SEM). Using the Lewis-Nielsen equation, experimental values of λ_c were compared with those predicted. The predicted results fit the experimental values well. The result showed that λ_c increases significantly when the filler content of composites is approximately over 50 vol %. Full article

(This article belongs to the Special Issue Thermal Properties and Applications of Polymers)

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9 pages, 21238 KiB

Open AccessArticle

Synthesis of Polystyrene Particles with Precisely Controlled Degree of Concaveness

by Wenhua Jing, Sinan Du and Zexin Zhang

Polymers 2018, 10(4), 458; https://doi.org/10.3390/polym10040458 - 21 Apr 2018

Cited by 14 | Viewed by 8051

Abstract

Shape is an essential property of polymeric particles. Herein, we propose a simple method to synthesize polymeric particles with a well-controlled concave shape. Our method takes advantage of the powerful seeded emulsion polymerization strategy with the well-known principle of “like dissolves like” in [...] Read more.

Shape is an essential property of polymeric particles. Herein, we propose a simple method to synthesize polymeric particles with a well-controlled concave shape. Our method takes advantage of the powerful seeded emulsion polymerization strategy with the well-known principle of “like dissolves like” in solvent chemistry. We first prepared polystyrene (PS) particles with a single dimple by seeded emulsion polymerization. Then the dimpled PS particles were dispersed in a dimethylformamide (DMF) and water mixture. Consequently, the non-crosslinked polymer chains inside the particle were dissolved by DMF, a good solvent for PS, and the PS chains migrated out of the particle, causing buckling of the dimple and enlargement of the concave. By systematic change of the fraction of DMF in the solvent mixture, we changed the amount of the dissolved PS chains, and achieved polymeric particles with precisely tuned degree of concaveness. These concave particles were found to readily self-assemble, driven by polymer-induced depletion interaction. The concave PS particles reported here provide potential building blocks for self-assembled polymeric materials, and new model systems for condensed matter research. Full article

(This article belongs to the Special Issue Precision Polymer Synthesis)

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12 pages, 5153 KiB

Open AccessFeature PaperArticle

Silk Composite with a Fluoropolymer as a Water-Resistant Protein-Based Material

by Keiji Numata, Nao Ifuku and Akira Isogai

Polymers 2018, 10(4), 459; https://doi.org/10.3390/polym10040459 - 21 Apr 2018

Cited by 9 | Viewed by 5975

Abstract

Silk-based materials are water-sensitive and show different physical properties at different humidities and under wet/dry conditions. To overcome the water sensitivity of silk-based materials, we developed a silk composite material with a fluoropolymer. Blending and coating the silk protein-based materials, such as films [...] Read more.

Silk-based materials are water-sensitive and show different physical properties at different humidities and under wet/dry conditions. To overcome the water sensitivity of silk-based materials, we developed a silk composite material with a fluoropolymer. Blending and coating the silk protein-based materials, such as films and textiles, with the fluoropolymer enhanced the surface hydrophobicity, water vapor barrier properties, and size stability during shrinkage tests. This material design with a protein biopolymer and a fluoropolymer is expected to broaden the applicability of protein-based materials. Full article

(This article belongs to the Special Issue Protein Biopolymer)

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13 pages, 5072 KiB

Open AccessArticle

Fabrication of Durably Superhydrophobic Cotton Fabrics by Atmospheric Pressure Plasma Treatment with a Siloxane Precursor

by Jing Yang, Yi Pu, Dagang Miao and Xin Ning

Polymers 2018, 10(4), 460; https://doi.org/10.3390/polym10040460 - 22 Apr 2018

Cited by 47 | Viewed by 7220

Abstract

The surface treatment of fabrics in an atmospheric environment may pave the way for commercially viable plasma modifications of fibrous matters. In this paper, we demonstrate a durably superhydrophobic cotton cellulose fabric prepared in a single-step graft polymerization of hexamethyldisiloxane (HMDSO) by N [...] Read more.

The surface treatment of fabrics in an atmospheric environment may pave the way for commercially viable plasma modifications of fibrous matters. In this paper, we demonstrate a durably superhydrophobic cotton cellulose fabric prepared in a single-step graft polymerization of hexamethyldisiloxane (HMDSO) by N₂ and O₂ atmospheric pressure plasma. We systematically investigated effects on contact angle (CA) and surface morphology of the cotton fabric under three operational parameters: precursor value; ionization gas flow rate; and plasma cycle time. Surface morphology, element composition, chemical structure and hydrophobic properties of the treated fabric were characterized by scanning electron microscope (SEM), EDS, FTIR and CA on the fabrics. The results indicated that a layer of thin film and nano-particles were evenly deposited on the cotton fibers, and graft polymerization occurred between cellulose and HMDSO. The fabric treated by O₂ plasma exhibited a higher CA of 162° than that treated by N₂ plasma which was about 149°. Furthermore, the CA of treated fabrics decreased only 0°~10° after storing at the ambient conditions for four months, and treated fabrics could also endure the standard textile laundering procedure in AATCC 61-2006 with minimum change. Therefore, this single-step plasma treatment method is shown to be a novel and environment-friendly way to make durable and superhydrophobic cotton fabrics. Full article

(This article belongs to the Special Issue Textile and Textile-Based Materials)

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18 pages, 3989 KiB

Open AccessArticle

Mussel-Inspired Polydopamine as a Green, Efficient, and Stable Platform to Functionalize Bamboo Fiber with Amino-Terminated Alkyl for High Performance Poly(butylene succinate) Composites

by Gonghua Hong, Haitao Cheng, Yang Meng, Jianyong Lin, Zhenghao Chen, Shuangbao Zhang and Wei Song

Polymers 2018, 10(4), 461; https://doi.org/10.3390/polym10040461 - 22 Apr 2018

Cited by 31 | Viewed by 8135

Abstract

A new and eco-friendly mussel-inspired surface modification pathway for bamboo fiber (BF) is presented in this study. The self-assembly polydopamine (PDA) coating can firmly adhere on BF surface, which also serves as a bridge to graft octadecylamine (ODA) for hydrophobic surface preparation. The [...] Read more.

A new and eco-friendly mussel-inspired surface modification pathway for bamboo fiber (BF) is presented in this study. The self-assembly polydopamine (PDA) coating can firmly adhere on BF surface, which also serves as a bridge to graft octadecylamine (ODA) for hydrophobic surface preparation. The as-formed PDA/ODA hybrid layer could supply abundant hydrophobic long-chain alkyls groups and generated a marked increase in BF surface roughness and a marked decrease in surface free energy. These changes provided advantages to improve fiber–matrix interfacial adhesion and wettability. Consequently, high performance was achieved by incorporating the hybrid modified BF into the polybutylene succinate (PBS) matrix. The resultant composite exhibited excellent mechanical properties, particularly tensile strength, which markedly increased by 77.2%. Meanwhile, considerable high water resistance with an absorption rate as low as 5.63% was also achieved. The gratifying macro-performance was primarily attributed to the excellent interfacial adhesion attained by hydrogen bonding and physical intertwining between the PDA/ODA coating on the BF and the PBS matrix, which was further determined by fracture morphology observations and dynamic mechanical analysis. Owing to the superior adhesive capacity of PDA, this mussel-inspired surface modification method may result in wide-ranging applications in polymer composites and be adapted to all natural fibers. Full article

(This article belongs to the Special Issue Modification of Natural Fibres to Improve Biocomposites Performances)

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13 pages, 2635 KiB

Open AccessArticle

Multienzyme Immobilized Polymeric Membrane Reactor for the Transformation of a Lignin Model Compound

by Rupam Sarma, Md. Saiful Islam, Mark P. Running and Dibakar Bhattacharyya

Polymers 2018, 10(4), 463; https://doi.org/10.3390/polym10040463 - 23 Apr 2018

Cited by 17 | Viewed by 5449

Abstract

We have developed an integrated, multienzyme functionalized membrane reactor for bioconversion of a lignin model compound involving enzymatic catalysis. The membrane bioreactors were fabricated through the layer-by-layer assembly approach to immobilize three different enzymes (glucose oxidase, peroxidase and laccase) into pH-responsive membranes. This [...] Read more.

We have developed an integrated, multienzyme functionalized membrane reactor for bioconversion of a lignin model compound involving enzymatic catalysis. The membrane bioreactors were fabricated through the layer-by-layer assembly approach to immobilize three different enzymes (glucose oxidase, peroxidase and laccase) into pH-responsive membranes. This novel membrane reactor couples the in situ generation of hydrogen peroxide (by glucose oxidase) to oxidative conversion of a lignin model compound, guaiacylglycerol-β-guaiacyl ether (GGE). Preliminary investigation of the efficacy of these functional membranes towards GGE degradation is demonstrated under convective flow mode. Over 90% of the initial feed could be degraded with the multienzyme immobilized membranes at a residence time of approximately 22 s. GGE conversion product analysis revealed the formation of oligomeric oxidation products upon reaction with peroxidase, which may be a potential hazard to membrane bioreactors. These oxidation products could further be degraded by laccase enzymes in the multienzymatic membranes, explaining the potential of multi enzyme membrane reactors. The multienzyme incorporated membrane reactors were active for more than 30 days of storage time at 4 °C. During this time span, repetitive use of the membrane reactor was demonstrated involving 5–6 h of operation time for each cycle. The membrane reactor displayed encouraging performance, losing only 12% of its initial activity after multiple cycles of operation. Full article

(This article belongs to the Special Issue Surface Modification and Functional Coatings for Polymers)

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Jump to: Research

29 pages, 5407 KiB

Open AccessFeature PaperReview

Chitin Deacetylases: Structures, Specificities, and Biotech Applications

by Laia Grifoll-Romero, Sergi Pascual, Hugo Aragunde, Xevi Biarnés and Antoni Planas

Polymers 2018, 10(4), 352; https://doi.org/10.3390/polym10040352 - 22 Mar 2018

Cited by 101 | Viewed by 10113

Abstract

Depolymerization and de-N-acetylation of chitin by chitinases and deacetylases generates a series of derivatives including chitosans and chitooligosaccharides (COS), which are involved in molecular recognition events such as modulation of cell signaling and morphogenesis, immune responses, and host-pathogen interactions. Chitosans and [...] Read more.

Depolymerization and de-N-acetylation of chitin by chitinases and deacetylases generates a series of derivatives including chitosans and chitooligosaccharides (COS), which are involved in molecular recognition events such as modulation of cell signaling and morphogenesis, immune responses, and host-pathogen interactions. Chitosans and COS are also attractive scaffolds for the development of bionanomaterials for drug/gene delivery and tissue engineering applications. Most of the biological activities associated with COS seem to be largely dependent not only on the degree of polymerization but also on the acetylation pattern, which defines the charge density and distribution of GlcNAc and GlcNH₂ moieties in chitosans and COS. Chitin de-N-acetylases (CDAs) catalyze the hydrolysis of the acetamido group in GlcNAc residues of chitin, chitosan, and COS. The deacetylation patterns are diverse, some CDAs being specific for single positions, others showing multiple attack, processivity or random actions. This review summarizes the current knowledge on substrate specificity of bacterial and fungal CDAs, focusing on the structural and molecular aspects of their modes of action. Understanding the structural determinants of specificity will not only contribute to unravelling structure-function relationships, but also to use and engineer CDAs as biocatalysts for the production of tailor-made chitosans and COS for a growing number of applications. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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47 pages, 16854 KiB

Open AccessReview

by Tatyana Ageyeva, Ilya Sibikin and József Karger-Kocsis

Polymers 2018, 10(4), 357; https://doi.org/10.3390/polym10040357 - 22 Mar 2018

Cited by 62 | Viewed by 12654

Abstract

This paper presents a comprehensive overview of polymers and related (nano)composites produced via anionic ring opening polymerization (AROP) of lactams. It was aimed at surveying and showing the important research and development results achieved in this field mostly over the last two decades. [...] Read more.

This paper presents a comprehensive overview of polymers and related (nano)composites produced via anionic ring opening polymerization (AROP) of lactams. It was aimed at surveying and showing the important research and development results achieved in this field mostly over the last two decades. This review covers the chemical background of the AROP of lactams, their homopolymers, copolymers, and in situ produced blends. The composites produced by AROP were grouped into nanocomposites, discontinuous fiber, continuous fiber, textile fabric, and self-reinforced composites. The manufacturing techniques were introduced and the most recent developments highlighted. Based on this state-of-art survey some future trends were deduced and as their “driving forces” novel and improved manufacturing techniques identified. Full article

(This article belongs to the Special Issue Polymer Hybrids and Composites)

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22 pages, 278 KiB

Open AccessReview

Internal and External Reinforcement of Concrete Members by Use of Shape Memory Alloy and Fiber Reinforced Polymers under Cyclic Loading—A Review

by Azadeh Parvin and Janet Raad

Polymers 2018, 10(4), 376; https://doi.org/10.3390/polym10040376 - 28 Mar 2018

Cited by 13 | Viewed by 5615

Abstract

This paper presents a review of recent studies on reinforced concrete (RC) structural components, such as beam-column joints (BCJs). These members are internally or externally reinforced with corrosion free shape memory alloy (SMA), fiber reinforced polymers (FRP), or a combination of the two [...] Read more.

This paper presents a review of recent studies on reinforced concrete (RC) structural components, such as beam-column joints (BCJs). These members are internally or externally reinforced with corrosion free shape memory alloy (SMA), fiber reinforced polymers (FRP), or a combination of the two materials. Bonded FRP sheets or near surface mounted (NSM) FRP bars are used in external strengthening cases. The use of FRP and SMA materials in RC structures can offer great potential benefits including lifetime cost saving, durability, safety, and post-earthquake serviceability for RC structures. Although FRP materials are well known for their corrosion resistance, high strength-to-weight ratios, ease of application, and constructability; SMA materials as reinforcement allow the structures to regain their original shape after the termination of the load without any permanent large residual deformation. In summary, the presented literature review provides an insight into the ongoing research on the use of these materials for retrofitting or strengthening of RC structural components and the trends for future research in this area. The cost and durability are also discussed. Full article

(This article belongs to the Special Issue Selected Papers from "SMAR 2017")

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14 pages, 300 KiB

Open AccessReview

Application of Chitin/Chitosan and Their Derivatives in the Papermaking Industry

by Zhaoping Song, Guodong Li, Feixiang Guan and Wenxia Liu

Polymers 2018, 10(4), 389; https://doi.org/10.3390/polym10040389 - 1 Apr 2018

Cited by 84 | Viewed by 11230

Abstract

Chitin/chitosan and their derivatives have become of great interest as functional materials in many fields within the papermaking industry. They have been employed in papermaking wet-end, paper surface coating, papermaking wastewater treatment, and other sections of the papermaking industry due to their structure [...] Read more.

Chitin/chitosan and their derivatives have become of great interest as functional materials in many fields within the papermaking industry. They have been employed in papermaking wet-end, paper surface coating, papermaking wastewater treatment, and other sections of the papermaking industry due to their structure and chemical properties. The purpose of this paper is to briefly discuss the application of chitin/chitosan and their derivatives in the papermaking industry. The development of their application in the papermaking area will be reviewed and summarized. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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16 pages, 3891 KiB

Open AccessReview

Development of Mucoadhesive Chitosan Derivatives for Use as Submucosal Injections

by Hidemi Hattori and Masayuki Ishihara

Polymers 2018, 10(4), 410; https://doi.org/10.3390/polym10040410 - 6 Apr 2018

Cited by 3 | Viewed by 5203

Abstract

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have been used for surgical treatment of early gastric cancer. These endoscopic techniques require proper submucosal injections beneath the tumor to provide a sufficiently high submucosal fluid cushion (SFC) to facilitate clean dissection and [...] Read more.

Endoscopic mucosal resection (EMR) and endoscopic submucosal dissection (ESD) have been used for surgical treatment of early gastric cancer. These endoscopic techniques require proper submucosal injections beneath the tumor to provide a sufficiently high submucosal fluid cushion (SFC) to facilitate clean dissection and resection of the tumor. Until now, the submucosal injection materials developed for endoscopic techniques such as EMR and ESD of tumors have been composed of macromolecules, proteins, or polysaccharides. We have been investigating the use of chitosan, a product that is obtained by the alkaline deacetylation of chitin, the second-most abundant natural polysaccharide. Specifically, we have been studying a photocrosslinked chitosan hydrogel (PCH) and solubilized chitosan derivatives for use as novel submucosal injections for endoscopic techniques. Notably, chitosan derivatives with lactose moieties linked to the amino groups of its glucosamine units can specifically interact with acidic mucopolysaccharides and mucins in submucosa without the need for the incorporation of harmful photoreactive groups nor potentially mutagenic ultraviolet irradiation. Full article

(This article belongs to the Collection Polysaccharides)

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26 pages, 44887 KiB

Open AccessReview

Stimuli-Responsive Microgels and Microgel-Based Systems: Advances in the Exploitation of Microgel Colloidal Properties and Their Interfacial Activity

by Garima Agrawal and Rahul Agrawal

Polymers 2018, 10(4), 418; https://doi.org/10.3390/polym10040418 - 9 Apr 2018

Cited by 70 | Viewed by 12132

Abstract

In this paper, recent developments in the chemical design of functional microgels are summarized. A wide range of available synthetic methods allows the incorporation of various reactive groups, charges, or biological markers inside the microgel network, thus controlling the deformation and swelling degree [...] Read more.

In this paper, recent developments in the chemical design of functional microgels are summarized. A wide range of available synthetic methods allows the incorporation of various reactive groups, charges, or biological markers inside the microgel network, thus controlling the deformation and swelling degree of the resulting smart microgels. These microgels can respond to various stimuli, such as temperature, pH, light, electric field, etc. and can show unique deformation behavior at the interface. Due to their switchability and interfacial properties, these smart microgels are being extensively explored for various applications, such as antifouling coatings, cell encapsulation, catalysis, controlled drug delivery, and tissue engineering. Full article

(This article belongs to the Special Issue Microgels and Hydrogels at Interfaces)

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26 pages, 53578 KiB

Open AccessReview

Aliphatic Polyester Nanofibers Functionalized with Cyclodextrins and Cyclodextrin-Guest Inclusion Complexes

by Ganesh Narayanan, Jialong Shen, Ramiz Boy, Bhupender S. Gupta and Alan E. Tonelli

Polymers 2018, 10(4), 428; https://doi.org/10.3390/polym10040428 - 11 Apr 2018

Cited by 29 | Viewed by 5351

Abstract

The fabrication of nanofibers by electrospinning has gained popularity in the past two decades; however, only in this decade, have polymeric nanofibers been functionalized using cyclodextrins (CDs) or their inclusion complexes (ICs). By combining electrospinning of polymers with free CDs, nanofibers can be [...] Read more.

The fabrication of nanofibers by electrospinning has gained popularity in the past two decades; however, only in this decade, have polymeric nanofibers been functionalized using cyclodextrins (CDs) or their inclusion complexes (ICs). By combining electrospinning of polymers with free CDs, nanofibers can be fabricated that are capable of capturing small molecules, such as wound odors or environmental toxins in water and air. Likewise, combining polymers with cyclodextrin-inclusion complexes (CD-ICs), has shown promise in enhancing or controlling the delivery of small molecule guests, by minor tweaking in the technique utilized in fabricating these nanofibers, for example, by forming core–shell or multilayered structures and conventional electrospinning, for controlled and rapid delivery, respectively. In addition to small molecule delivery, the thermomechanical properties of the polymers can be significantly improved, as our group has shown recently, by adding non-stoichiometric inclusion complexes to the polymeric nanofibers. We recently reported and thoroughly characterized the fabrication of polypseudorotaxane (PpR) nanofibers without a polymeric carrier. These PpR nanofibers show unusual rheological and thermomechanical properties, even when the coverage of those polymer chains is relatively sparse (~3%). A key advantage of these PpR nanofibers is the presence of relatively stable hydroxyl groups on the outer surface of the nanofibers, which can subsequently be taken advantage of for bioconjugation, making them suitable for biomedical applications. Although the number of studies in this area is limited, initial results suggest significant potential for bone tissue engineering, and with additional bioconjugation in other areas of tissue engineering. In addition, the behaviors and uses of aliphatic polyester nanofibers functionalized with CDs and CD-ICs are briefly described and summarized. Based on these observations, we attempt to draw conclusions for each of these combinations, and the relationships that exist between their presence and the functional behaviors of their nanofibers. Full article

(This article belongs to the Collection Polysaccharides)

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51 pages, 21605 KiB

Open AccessReview

Chitosan in Non-Viral Gene Delivery: Role of Structure, Characterization Methods, and Insights in Cancer and Rare Diseases Therapies

by Beatriz Santos-Carballal, Elena Fernández Fernández and Francisco M. Goycoolea

Polymers 2018, 10(4), 444; https://doi.org/10.3390/polym10040444 - 15 Apr 2018

Cited by 87 | Viewed by 11348

Abstract

Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver [...] Read more.

Non-viral gene delivery vectors have lagged far behind viral ones in the current pipeline of clinical trials of gene therapy nanomedicines. Even when non-viral nanovectors pose less safety risks than do viruses, their efficacy is much lower. Since the early studies to deliver pDNA, chitosan has been regarded as a highly attractive biopolymer to deliver nucleic acids intracellularly and induce a transgenic response resulting in either upregulation of protein expression (for pDNA, mRNA) or its downregulation (for siRNA or microRNA). This is explained as the consequence of a multi-step process involving condensation of nucleic acids, protection against degradation, stabilization in physiological conditions, cellular internalization, release from the endolysosome (“proton sponge” effect), unpacking and enabling the trafficking of pDNA to the nucleus or the siRNA to the RNA interference silencing complex (RISC). Given the multiple steps and complexity involved in the gene transfection process, there is a dearth of understanding of the role of chitosan’s structural features (M_w and degree of acetylation, DA%) on each step that dictates the net transfection efficiency and its kinetics. The use of fully characterized chitosan samples along with the utilization of complementary biophysical and biological techniques is key to bridging this gap of knowledge and identifying the optimal chitosans for delivering a specific gene. Other aspects such as cell type and administration route are also at play. At the same time, the role of chitosan structural features on the morphology, size and surface composition of synthetic virus-like particles has barely been addressed. The ongoing revolution brought about by the recent discovery of CRISPR-Cas9 technology will undoubtedly be a game changer in this field in the short term. In the field of rare diseases, gene therapy is perhaps where the greatest potential lies and we anticipate that chitosans will be key players in the translation of research to the clinic. Full article

(This article belongs to the Special Issue Advances in Chitin/Chitosan Characterization and Applications)

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17 pages, 3239 KiB

Open AccessReview

Biomedical Applications of Chitosan and Its Derivative Nanoparticles

by Dongying Zhao, Shuang Yu, Beini Sun, Shuang Gao, Sihan Guo and Kai Zhao

Polymers 2018, 10(4), 462; https://doi.org/10.3390/polym10040462 - 23 Apr 2018

Cited by 389 | Viewed by 20661

Abstract

Chitosan is a biodegradable natural polymer with many advantages such as nontoxicity, biocompatibility, and biodegradability. It can be applied in many fields, especially in medicine. As a delivery carrier, it has great potential and cannot be compared with other polymers. Chitosan is extremely [...] Read more.

Chitosan is a biodegradable natural polymer with many advantages such as nontoxicity, biocompatibility, and biodegradability. It can be applied in many fields, especially in medicine. As a delivery carrier, it has great potential and cannot be compared with other polymers. Chitosan is extremely difficult to solubilize in water, but it can be solubilized in acidic solution. Its insolubility in water is a major limitation for its use in medical applications. Chitosan derivatives can be obtained by chemical modification using such techniques as acylation, alkylation, sulfation, hydroxylation, quaternization, esterification, graft copolymerization, and etherification. Modified chitosan has chemical properties superior to unmodified chitosan. For example, nanoparticles produced from chitosan derivatives can be used to deliver drugs due to their stability and biocompatibility. This review mainly focuses on the properties of chitosan, chitosan derivatives, and the origin of chitosan-based nanoparticles. In addition, applications of chitosan-based nanoparticles in drug delivery, vaccine delivery, antimicrobial applications, and callus and tissue regeneration are also presented. In summary, nanoparticles based on chitosan have great potential for research and development of new nano vaccines and nano drugs in the future. Full article

(This article belongs to the Collection Polysaccharides)

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Polymers, Volume 10, Issue 4 (April 2018) – 121 articles

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