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

Cover Story (view full-size image): Chitin deacetylases (CDAs) catalyze the hydrolysis of acetamido groups in GlcNAc residues of chitin, chitosan, and chitooligosaccharides (COS). The deacetylation specificity exhibited by CDAs is diverse, some enzymes being specific for single positions, others showing multiple attacks, processivity or random actions. The “subsite capping model” proposes that specificity is partly governed by a series of dynamic loops that shape the substrate binding cleft, which differ among CDAs on a highly conserved protein core. The structures, specificities, and biotech applications of bacterial and fungal CDAs are reviewed here. View the paper here.
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13 pages, 2635 KiB  
Article
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 5740
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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17 pages, 3239 KiB  
Review
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 438 | Viewed by 22232
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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18 pages, 3989 KiB  
Article
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 34 | Viewed by 8600
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, 5072 KiB  
Article
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 51 | Viewed by 7584
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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12 pages, 5153 KiB  
Article
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 6428
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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9 pages, 21238 KiB  
Article
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 8588
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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11 pages, 4724 KiB  
Article
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 22 | Viewed by 9524
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 (λc) of composites. Composites with different filler particle sizes, filler contents and filler geometry were fabricated and the influence of these variables on the λc was studied. The λc 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 λc were compared with those predicted. The predicted results fit the experimental values well. The result showed that λc 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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16 pages, 4425 KiB  
Article
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 8884
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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18 pages, 3400 KiB  
Article
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 21 | Viewed by 5397
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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13 pages, 2474 KiB  
Article
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 4421
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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10 pages, 2804 KiB  
Article
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 4386
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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19 pages, 3389 KiB  
Article
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 70 | Viewed by 9724
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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23 pages, 4141 KiB  
Article
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 19 | Viewed by 5270
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, 9074 KiB  
Article
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 4263
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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12 pages, 2107 KiB  
Article
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 37 | Viewed by 10634
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 (T5 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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12 pages, 26061 KiB  
Article
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 16 | Viewed by 5619
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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14 pages, 901 KiB  
Article
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 4731
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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15 pages, 4785 KiB  
Article
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 8884
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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12 pages, 5824 KiB  
Article
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 6091
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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51 pages, 21605 KiB  
Review
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 96 | Viewed by 11799
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 (Mw 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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15 pages, 26414 KiB  
Article
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 5635
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 (pKb) 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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15 pages, 3525 KiB  
Article
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 43 | Viewed by 6907
Abstract
In this paper, we compared the transfection efficiency and cytotoxicity of methylglycol-chitosan (MG-CS) and diethylaminoethyl-chitosan (DEAE-CSI and DEAE-CSII 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-CSI and DEAE-CSII 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-CSI and DEAE-CSII 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-CSI and DEAE-CSII 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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14 pages, 14702 KiB  
Article
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 13 | Viewed by 5135
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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16 pages, 5779 KiB  
Article
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 5627
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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13 pages, 4822 KiB  
Article
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 27 | Viewed by 10428
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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10 pages, 20156 KiB  
Article
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 29 | Viewed by 6934
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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14 pages, 17547 KiB  
Article
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 23 | Viewed by 5030
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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12 pages, 3596 KiB  
Article
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 5642
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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12 pages, 23020 KiB  
Article
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 4901
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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17 pages, 8619 KiB  
Article
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 10 | Viewed by 4615
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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