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Polymers, Volume 9, Issue 5 (May 2017)

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Cover Story The copolymerization of 4-pentenoic acid and (-)-perillic acid-based pentafluorophenyl active [...] Read more.
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Open AccessArticle Development of Defatted Soy Flour-Based Adhesives by Acid Hydrolysis of Carbohydrates
Polymers 2017, 9(5), 153; doi:10.3390/polym9050153
Received: 16 March 2017 / Revised: 8 April 2017 / Accepted: 18 April 2017 / Published: 25 April 2017
Cited by 1 | PDF Full-text (12762 KB) | HTML Full-text | XML Full-text
Abstract
Soy-based adhesives are attracting increasing attention in recent years because they are a renewable and environmentally friendly raw material. Defatted soy flour (DSF), comprised of 50% protein and 40% carbohydrate, is the most widely used raw material for the preparation of soy-based adhesives
[...] Read more.
Soy-based adhesives are attracting increasing attention in recent years because they are a renewable and environmentally friendly raw material. Defatted soy flour (DSF), comprised of 50% protein and 40% carbohydrate, is the most widely used raw material for the preparation of soy-based adhesives that are unfortunately hampered by poor gluability and water resistance. In the present study, we developed a self-crosslinking approach to prepare a formaldehyde-free defatted soy flour-based adhesive (SBA). Carbohydrates in the DSF were hydrolyzed with 0% (controls), 0.5%, 1.0%, 2.0%, 3.0% and 5.0% hydrochloric acid, and cross-linked with proteins to prepare the SBA. The effect of hydrolyzed carbohydrates on the performance of the SBA was investigated, and hydrolyzed carbohydrates significantly increased the amount of reducing sugars, but decreased insoluble substances. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses revealed an enhanced cross-linking structure with fewer hydrophilic groups in cured SBAs. Maillard reactions between hydrolyzed carbohydrates and proteins resulted in SBAs with better gluability, rheological properties and thermal stability than controls. Scanning electron microscopy (SEM) images showed that plywood bonded with SBA had a higher wood failure rate than controls. This approach has potential for preparing bio-adhesives with enhanced properties from other natural resources with a similar polysaccharides and protein composition. Full article
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Open AccessArticle Surface Patterning of Gold Nanoparticles on PEG-Based Hydrogels to Control Cell Adhesion
Polymers 2017, 9(5), 154; doi:10.3390/polym9050154
Received: 31 March 2017 / Revised: 18 April 2017 / Accepted: 21 April 2017 / Published: 26 April 2017
Cited by 2 | PDF Full-text (7081 KB) | HTML Full-text | XML Full-text
Abstract
We report on a versatile and easy approach to micro-pattern gold nanoparticles (Au NPs) on 8-arm poly(ethylene glycol)-vinyl sulfone thiol (8PEG-VS-SH) hydrogels, and the application of these patterned Au NPs stripes in controlling cell adhesion. Firstly, the Au NPs were patterned on silicon
[...] Read more.
We report on a versatile and easy approach to micro-pattern gold nanoparticles (Au NPs) on 8-arm poly(ethylene glycol)-vinyl sulfone thiol (8PEG-VS-SH) hydrogels, and the application of these patterned Au NPs stripes in controlling cell adhesion. Firstly, the Au NPs were patterned on silicon wafers, and then they were transferred onto reactive, multifunctional 8PEG-VS-SH hydrogels. The patterned, micrometer-sized Au NPs stripes with variable spacings ranging from 20 μm to 50 μm were created by our recently developed micro-contact deprinting method. For this micro-contact deprinting approach, four different PEG-based stamp materials have been tested and it was found that the triblock copolymer PEG-PPG-PEG-(3BC) stamp established the best transfer efficiency and has been used in the ongoing work. After the successful creation of micro-patterns of Au NPs stripes on silicon, the patterns can be transferred conveniently and accurately to 8PEG-VS-SH hydrogel films. Subsequently these Au NPs patterns on 8PEG-VS-SH hydrogels have been investigated in cell culture with murine fibroblasts (L-929). The cells have been observed to adhere to and spread on those nano-patterned micro-lines in a remarkably selective and ordered manner. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
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Open AccessArticle Systematic Study of a Library of PDMAEMA-Based, Superparamagnetic Nano-Stars for the Transfection of CHO-K1 Cells
Polymers 2017, 9(5), 156; doi:10.3390/polym9050156
Received: 16 January 2017 / Revised: 7 April 2017 / Accepted: 24 April 2017 / Published: 28 April 2017
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Abstract
The introduction of the DNA into mammalian cells remains a challenge in gene delivery, particularly in vivo. Viral vectors are unmatched in their efficiency for gene delivery, but may trigger immune responses and cause severe side-reactions. Non-viral vectors are much less efficient. Recently,
[...] Read more.
The introduction of the DNA into mammalian cells remains a challenge in gene delivery, particularly in vivo. Viral vectors are unmatched in their efficiency for gene delivery, but may trigger immune responses and cause severe side-reactions. Non-viral vectors are much less efficient. Recently, our group has suggested that a star-shaped structure improves and even transforms the gene delivery capability of synthetic polycations. In this contribution, this effect was systematically studied using a library of highly homogeneous, paramagnetic nano-star polycations with varied arm lengths and grafting densities. Gene delivery was conducted in CHO-K1 cells, using a plasmid encoding a green fluorescent reporter protein. Transfection efficiencies and cytotoxicities varied systematically with the nano-star architecture. The arm density was particularly important, with values of approximately 0.06 arms/nm2 yielding the best results. In addition, a certain fraction of the cells became magnetic during transfection. The gene delivery potential of a nano-star and its ability to render the cells magnetic did not have any correlations. End-capping the polycation arms with di(ethylene glycol) methyl ether methacrylate (PDEGMA) significantly improved serum compatibility under transfection conditions; such nano-stars are potential candidates for future in vivo testing. Full article
(This article belongs to the Special Issue Polymers and Nanogels for Gene Therapy)
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Open AccessArticle A Strategy to Enhance the Electrode Performance of Novel Three-Dimensional PEDOT/RVC Composites by Electrochemical Deposition Method
Polymers 2017, 9(5), 157; doi:10.3390/polym9050157
Received: 27 March 2017 / Revised: 20 April 2017 / Accepted: 25 April 2017 / Published: 28 April 2017
Cited by 1 | PDF Full-text (9718 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this article, three-dimensional (3D) microstuctured poly(3,4-ethylenedioxythiophene) (PEDOT)/reticulated vitreous carbon (RVC) composite electrodes with varying amount of PEDOT loadings were successfully prepared by electrochemical deposition method. The composites were characterized by Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and cyclic voltammetry.
[...] Read more.
In this article, three-dimensional (3D) microstuctured poly(3,4-ethylenedioxythiophene) (PEDOT)/reticulated vitreous carbon (RVC) composite electrodes with varying amount of PEDOT loadings were successfully prepared by electrochemical deposition method. The composites were characterized by Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and cyclic voltammetry. Raman spectra suggest that there is a strong interaction between the RVC and backbone of PEDOT chain. It is revealed from the SEM images that the PEDOT amount, thickness, surface roughness, porosity, and globular structure on RVC electrode are increased with the increase in polymerization time. The capacitance of PEDOT/RVC electrode has increased by a factor of 2230 compared to a bare RVC electrode when polymerization is carried out for 120 min. Moreover, the capacitance of PEDOT was found to be very high compared with other PEDOT studies. The electrodes also show good cyclic stability. This substantial increase in capacitance of RVC electrode is due to the rough, highly porous, and honeycomb-like fine structure of PEDOT coating, which shows a flower-like morphology, consisting of numerous thin flakes with numbers of macropores and micropores. This interesting morphology has enhanced the performance of PEDOT because of increased electrode surface area, specific capacitance, and macroporous structure of RVC electrode. Full article
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Open AccessArticle CAGW Peptide Modified Biodegradable Cationic Copolymer for Effective Gene Delivery
Polymers 2017, 9(5), 158; doi:10.3390/polym9050158
Received: 8 March 2017 / Revised: 11 April 2017 / Accepted: 24 April 2017 / Published: 28 April 2017
Cited by 3 | PDF Full-text (6198 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, gene therapy has become a promising technology to enhance endothelialization of artificial vascular grafts. The ideal gene therapy requires a gene carrier with low cytotoxicity and high transfection efficiency. In this paper, we prepared a biodegradable cationic copolymer poly(d,l
[...] Read more.
In recent years, gene therapy has become a promising technology to enhance endothelialization of artificial vascular grafts. The ideal gene therapy requires a gene carrier with low cytotoxicity and high transfection efficiency. In this paper, we prepared a biodegradable cationic copolymer poly(d,l-lactide-co-glycolide)-graft-PEI (PLGA-g-PEI), grafted Cys-Ala-Gly-Trp (CAGW) peptide onto this copolymer via the thiol-ene Click-reaction, and then prepared micelles by a self-assembly method. pEGFP-ZNF580 plasmids (pDNA) were condensed by these micelles via electrostatic interaction to form gene complexes. The CAGW peptide enables these gene complexes with special recognition for endothelial cells, which could enhance their transfection. As a gene carrier system, the PLGA-g-PEI-g-CAGW/pDNA gene complexes were evaluated and the results showed that they had suitable diameter and zeta potential for cellular uptake, and exhibited low cytotoxicity and high transfection efficiency for EA.hy926 cells. Full article
(This article belongs to the Special Issue Polymers and Nanogels for Gene Therapy)
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Open AccessArticle A Modified Ceramic-Coating Separator with High-Temperature Stability for Lithium-Ion Battery
Polymers 2017, 9(5), 159; doi:10.3390/polym9050159
Received: 28 March 2017 / Revised: 24 April 2017 / Accepted: 25 April 2017 / Published: 29 April 2017
Cited by 1 | PDF Full-text (20523 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this work, the ceramic coating separator (CCS-CS) prepared with polyethylene (PE) separator, Al2O3 inorganic particles, carboxymethyl cellulose sodium (CMC) and styrene-butadiene rubber (SBR) mix binders is further modified by coating with a thin polydopamine (PDA) layer through a simple
[...] Read more.
In this work, the ceramic coating separator (CCS-CS) prepared with polyethylene (PE) separator, Al2O3 inorganic particles, carboxymethyl cellulose sodium (CMC) and styrene-butadiene rubber (SBR) mix binders is further modified by coating with a thin polydopamine (PDA) layer through a simple chemical deposition method. Compared with the bare ceramic coating separator, the PDA-modified CCS-CS (CCS-CS-PDA) exhibits excellent thermal stability, which shows no thermal shrinkage after storing at 200 °C for 30 min. Compared with the PE separator, both the uptake and wettability with the electrolyte and water of CCS-CS-PDA are improved significantly. Meanwhile, when saturated with liquid electrolyte, the CCS-CS-PDA also shows enabled high ionic conductance. Furthermore, the test of the electrochemical impedances changing with the temperatures suggests that only the PE separator exhibits no thermal shutdown behaviors, and the CCS-CS separator only has a shutdown temperature range from 138 to 160 °C, while the CCS-CS-PDA shows a shutdown temperature range from 138 to more than 200 °C. The cells prepared with the CCS-CS-PDA also show stable repeated cycling performance and good rate capacity at room temperature. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessArticle Highly Branched poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) for High Performance Gene Transfection
Polymers 2017, 9(5), 161; doi:10.3390/polym9050161
Received: 15 March 2017 / Revised: 26 April 2017 / Accepted: 27 April 2017 / Published: 1 May 2017
Cited by 2 | PDF Full-text (1237 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The top-performing linear poly(β-amino ester) (LPAE), poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) (C32), has demonstrated gene transfection efficiency comparable to viral-mediated gene delivery. Herein, we report the synthesis of a series of highly branched poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) (HC32) and explore how the branching structure influences the performance of
[...] Read more.
The top-performing linear poly(β-amino ester) (LPAE), poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) (C32), has demonstrated gene transfection efficiency comparable to viral-mediated gene delivery. Herein, we report the synthesis of a series of highly branched poly(5-amino-1-pentanol-co-1,4-butanediol diacrylate) (HC32) and explore how the branching structure influences the performance of C32 in gene transfection. HC32 were synthesized by an “A2 + B3 + C2” Michal addition strategy. Gaussia luciferase (Gluciferase) and green fluorescent protein (GFP) coding plasmid DNA were used as reporter genes and the gene transfection efficiency was evaluated in human cervical cancer cell line (HeLa) and human recessive dystrophic epidermolysis bullosa keratinocyte (RDEBK) cells. We found that the optimal branching structure led to a much higher gene transfection efficiency in comparison to its linear counterpart and commercial reagents, while preserving high cell viability in both cell types. The branching strategy affected DNA binding, proton buffering capacity and degradation of polymers as well as size, zeta potential, stability, and DNA release rate of polyplexes significantly. Polymer degradation and DNA release rate played pivotal parts in achieving the high gene transfection efficiency of HC32-103 polymers, providing new insights for the development of poly(β-amino ester)s-based gene delivery vectors. Full article
(This article belongs to the Special Issue Polymers and Nanogels for Gene Therapy)
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Open AccessArticle Synthesis, Characterization and the Solvent Effects on Interfacial Phenomena of Jatropha Curcas Oil Based Non-Isocyanate Polyurethane
Polymers 2017, 9(5), 162; doi:10.3390/polym9050162
Received: 27 March 2017 / Revised: 19 April 2017 / Accepted: 25 April 2017 / Published: 1 May 2017
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Abstract
Non-isocyanate polyurethane (NIPU) was prepared from Jatropha curcas oil (JCO) and its alkyd resin via curing with different diamines. The isocyanate-free approach is a green chemistry route, wherein carbon dioxide conversion plays a major role in NIPU preparation. Catalytic carbon dioxide fixation can
[...] Read more.
Non-isocyanate polyurethane (NIPU) was prepared from Jatropha curcas oil (JCO) and its alkyd resin via curing with different diamines. The isocyanate-free approach is a green chemistry route, wherein carbon dioxide conversion plays a major role in NIPU preparation. Catalytic carbon dioxide fixation can be achieved through carbonation of epoxidized derivatives of JCO. In this study, 1,3-diaminopropane (DM) and isophorone diamine (IPDA) were used as curing agents separately. Cyclic carbonate conversion was catalyzed by tetrabutylammonium bromide. After epoxy conversion, carbonated JCO (CJCO) and carbonated alkyd resin (CC-AR) with carbonate contents of 24.9 and 20.2 wt %, respectively, were obtained. The molecular weight of CJCO and CC-AR were determined by gel permeation chromatography. JCO carbonates were cured with different amine contents. CJCO was blended with different weight ratios of CC-AR to improve its characteristics. The cured NIPU film was characterized by spectroscopic techniques, differential scanning calorimetry, and a universal testing machine. Field emission scanning electron microscopy was used to analyze the morphology of the NIPU film before and after solvent treatment. The solvent effects on the NIPU film interfacial surface were investigated with water, 30% ethanol, methyl ethyl ketone, 10% HCl, 10% NaCl, and 5% NaOH. NIPU based on CCJO and CC-AR (ratio of 1:3) with IPDA crosslink exhibits high glass transition temperature (44 °C), better solvent and chemical resistance, and Young’s modulus (680 MPa) compared with the blend crosslinked with DM. Thus, this study showed that the presence of CC-AR in CJCO-based NIPU can improve the thermomechanical and chemical resistance performance of the NIPU film via a green technology approach. Full article
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Open AccessArticle Manufacturing and Characterization of Novel Electrospun Composite Comprising Polyurethane and Mustard Oil Scaffold with Enhanced Blood Compatibility
Polymers 2017, 9(5), 163; doi:10.3390/polym9050163
Received: 18 March 2017 / Revised: 25 April 2017 / Accepted: 28 April 2017 / Published: 4 May 2017
Cited by 2 | PDF Full-text (1945 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this work is to characterize and investigate the blood compatibility of polyurethane (PU)/mustard oil composites fabricated using electrospinning technique. The fabricated scaffold was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), thermogravimetric analysis
[...] Read more.
The objective of this work is to characterize and investigate the blood compatibility of polyurethane (PU)/mustard oil composites fabricated using electrospinning technique. The fabricated scaffold was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and contact angle measurements. The activated partial thromboplastin time (APPT), prothrombin time (PT) and the hemolytic assay were done to investigate the blood compatibility of the developed composites. The SEM results revealed that the fiber diameter of the composites (761 ± 123 nm) was reduced compared to pristine PU control. The interaction between PU and mustard oil was confirmed by FTIR as evident through the shifting of peaks. The fabricated composites depicted hydrophobic behavior as insinuated by the increase in contact angle measurements. PU/mustard composites displayed improved crystallinity as confirmed by TGA. Atomic force micrographs suggested that developed PU/mustard oil composites showed an increase in the surface roughness (Ra) compared to pure PU. The Ra of pure PU was observed to be 723 nm but for the fabricated PU/mustard oil composite the Ra was found to be 1298 nm (Ra). The hemolytic index value for pure PU and fabricated composites was observed to be 2.73% and 1.15% indicating that developed composites showed a non-hemolytic behavior signifying the safety of the composites with red blood cells. Hence the newly developed composites with improved physicochemical and blood compatibility properties may be considered as a potential candidate for fabricating cardiac patches and grafts. Full article
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Open AccessArticle Syneresis in Gels of Highly Ferulated Arabinoxylans: Characterization of Covalent Cross-Linking, Rheology, and Microstructure
Polymers 2017, 9(5), 164; doi:10.3390/polym9050164
Received: 30 March 2017 / Revised: 28 April 2017 / Accepted: 2 May 2017 / Published: 5 May 2017
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Abstract
Arabinoxylans (AXs) with high ferulic acid (FA) content (7.18 µg/mg AXs) were cross-linked using laccase. Storage (G’) modulus of AX solutions at 1% (AX-1) and 2% (AX-2) (w/v) registered maximum values of 409 Pa and 889 Pa
[...] Read more.
Arabinoxylans (AXs) with high ferulic acid (FA) content (7.18 µg/mg AXs) were cross-linked using laccase. Storage (G’) modulus of AX solutions at 1% (AX-1) and 2% (AX-2) (w/v) registered maximum values of 409 Pa and 889 Pa at 180 min and 83 min, respectively. Atomic force microscopy revealed the grained and irregular surface of the AX-1 gel and the smoother surface without significant depressions of the AX-2 gel. Cured AX gels exhibited a liquid phase surrounding the samples indicating syneresis. The syneresis ratio percentage (% Rs) of the gels was registered over time reaching stabilization at 20 h. The % Rs was not significantly different between AX-1 (60.0%) and AX-2 (62.8%) gels. After 20 h of syneresis development, the dimers of the FA in the AX-1 and AX-2 gels significantly increased by 9% and 78%, respectively; moreover, the trimers of the FA in the AX-1 and AX-2 gels, by 94% and 300%, respectively. Scanning electron microscopy showed that, after syneresis stabilization, AX gels presented a more compact microstructure. Syneresis development in the gels of highly ferulated AXs could be related to the polymer network contraction due to the additional formation of dimers and trimers of the FA (cross-linking structures), which may act like a “zipping” process, increasing the polymer chains′ connectivity. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
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Open AccessArticle Effect of Maleic Anhydride-Modified Poly(lactic acid) on the Properties of Its Hybrid Fiber Biocomposites
Polymers 2017, 9(5), 165; doi:10.3390/polym9050165
Received: 25 March 2017 / Revised: 26 April 2017 / Accepted: 2 May 2017 / Published: 5 May 2017
Cited by 1 | PDF Full-text (1945 KB) | HTML Full-text | XML Full-text
Abstract
This work investigated the effect of maleic anhydride (MA)-modified poly(lactic acid) (PLA), which is melt-blended with different untreated and aqueous borax (BR)-treated hybrid oil palm empty fruit bunch fibers (EFBF)/Kenaf core fibers (KCF), and compression-molded into corresponding hybrid biocomposites. These hybrid systems includes
[...] Read more.
This work investigated the effect of maleic anhydride (MA)-modified poly(lactic acid) (PLA), which is melt-blended with different untreated and aqueous borax (BR)-treated hybrid oil palm empty fruit bunch fibers (EFBF)/Kenaf core fibers (KCF), and compression-molded into corresponding hybrid biocomposites. These hybrid systems includes BR-treated EFBF/BR-treated KCF reinforced MA-modified PLA i.e., BR(EFBF-KCF)-MAPLA, BR-treated EFBF/BR-treated KCF reinforced unmodified PLA i.e., BR(EFBF-KCF)-PLA, untreated EFBF/untreated KCF reinforced MA-modified PLA i.e., EFBF-KCF-MAPLA, and untreated EFBF/untreated KCF reinforced unmodified PLA i.e., EFBF-KCF-PLA respectively. Characterizations of the hybrid systems revealed that optimal mechanical, physical, morphological, thermal and dynamic mechanical properties were provided by the BR(EFBF-KCF)-MAPLA, resulting from improved interface adhesion, consequent of the synergistic influence of BR treatment of natural fibers, and the compatibilization effect provided by the MA-modified PLA. The grafting degree and efficiency of MA onto the PLA backbone was appreciable, as indicated by direct titration, and through monitoring using Fourier Transform Infrared Spectroscopy (FTIR); thus the MA-modified PLA facilitated the formation of strong interface adhesion with the BR-treated hybrid fibers. The BR(EFBF-KCF)-MAPLA showed promising properties for usage as a bio-inspired, and sustainable alternative fiberboard article. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
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Open AccessFeature PaperArticle Synthesis and Functionalization of Periodic Copolymers
Polymers 2017, 9(5), 166; doi:10.3390/polym9050166
Received: 31 March 2017 / Revised: 28 April 2017 / Accepted: 2 May 2017 / Published: 6 May 2017
PDF Full-text (1613 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
For the copolymerization of non-conjugated olefins and maleimides, it is known that under certain conditions periodic ABA monomer sequences are formed. In this work, such a copolymerization is used to create polymers which have defined (periodic) monomer sequences and can be functionalized after
[...] Read more.
For the copolymerization of non-conjugated olefins and maleimides, it is known that under certain conditions periodic ABA monomer sequences are formed. In this work, such a copolymerization is used to create polymers which have defined (periodic) monomer sequences and can be functionalized after polymerization. The copolymerization of pentafluorophenol (PFP) active esters of 4-pentenoic acid and perillic acid with N-phenyl maleimide (PhMI) was studied in 1,2-dichloroethane (DCE) and 1,1,1,3,3,3-hexafluoro-2-phenyl-2-propanol (HFPP). In DCE and for the copolymerization of the PFP ester of 4-pentenoic acid and PhMI in HFPP, polymers were formed where the active esters were separated by at least one PhMI unit. The average number of separating PhMI units can be controlled by varying the feed ratio of the monomers. For the copolymerization of the PFP ester of perillic acid in HFPP, a preference for the formation of periodic copolymers was observed, where active esters were preferably separated from each other by a maximum of two PhMI moieties. Therefore, the copolymerization of said active ester containing monomers with PhMI provides a platform to create polymers in which reactive moieties are distributed along the polymer chain in different fashions. The active esters in the non-conjugated vinyl monomers could be used in a post-polymerization functionalization step to create functionalized polymers with defined monomer sequences in a modular way. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
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Open AccessArticle A High-Performance Soy Protein Isolate-Based Nanocomposite Film Modified with Microcrystalline Cellulose and Cu and Zn Nanoclusters
Polymers 2017, 9(5), 167; doi:10.3390/polym9050167
Received: 31 March 2017 / Revised: 1 May 2017 / Accepted: 3 May 2017 / Published: 6 May 2017
Cited by 5 | PDF Full-text (6431 KB) | HTML Full-text | XML Full-text
Abstract
Soy protein isolate (SPI)-based materials are abundant, biocompatible, renewable, and biodegradable. In order to improve the tensile strength (TS) of SPI films, we prepared a novel composite film modified with microcrystalline cellulose (MCC) and metal nanoclusters (NCs) in this study. The effects of
[...] Read more.
Soy protein isolate (SPI)-based materials are abundant, biocompatible, renewable, and biodegradable. In order to improve the tensile strength (TS) of SPI films, we prepared a novel composite film modified with microcrystalline cellulose (MCC) and metal nanoclusters (NCs) in this study. The effects of the modification of MCC on the properties of SPI-Cu NCs and SPI-Zn NCs films were investigated. Attenuated total reflectance-Fourier transformed infrared spectroscopy analyses and X-ray diffraction patterns characterized the strong interactions and reduction of the crystalline structure of the composite films. Scanning electron microscopy (SEM) showed the enhanced cross-linked and entangled structure of modified films. Compared with an untreated SPI film, the tensile strength of the SPI-MCC-Cu and SPI-MCC-Zn films increased from 2.91 to 13.95 and 6.52 MPa, respectively. Moreover, the results also indicated their favorable water resistance with a higher water contact angle. Meanwhile, the composite films exhibited increased initial degradation temperatures, demonstrating their higher thermostability. The results suggested that MCC could effectively improve the performance of SPI-NCs films, which would provide a novel preparation method for environmentally friendly SPI-based films in the applications of packaging materials. Full article
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Open AccessArticle Influence of Ligand Backbone Structure and Connectivity on the Properties of Phosphine-Sulfonate Pd(II)/Ni(II) Catalysts
Polymers 2017, 9(5), 168; doi:10.3390/polym9050168
Received: 1 April 2017 / Revised: 28 April 2017 / Accepted: 3 May 2017 / Published: 9 May 2017
Cited by 2 | PDF Full-text (3173 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Phosphine-sulfonate based palladium and nickel catalysts have been extensively studied in ethylene polymerization and copolymerization reactions. Previously, the majority of the research works focused on the modifications of the substituents on the phosphorous atom. In this contribution, we systematically demonstrated that the change
[...] Read more.
Phosphine-sulfonate based palladium and nickel catalysts have been extensively studied in ethylene polymerization and copolymerization reactions. Previously, the majority of the research works focused on the modifications of the substituents on the phosphorous atom. In this contribution, we systematically demonstrated that the change of the ligand backbone from benzene to naphthalene could greatly improve the properties of this class of catalysts. In the palladium system, this change could increase catalyst stability and polyethylene molecular weights. In the nickel system, this change could dramatically increase the polyethylene molecular weights. Most interestingly, the change in the connectivity of phosphine and sulfonate moieties to the naphthalene backbone could also significantly influence the catalyst properties. Full article
(This article belongs to the Special Issue Olefin Polymerization and Polyolefin)
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Open AccessArticle Soy-Based Adhesive Cross-Linked by Phenol-Formaldehyde-Glutaraldehyde
Polymers 2017, 9(5), 169; doi:10.3390/polym9050169
Received: 10 March 2017 / Revised: 2 May 2017 / Accepted: 5 May 2017 / Published: 8 May 2017
Cited by 1 | PDF Full-text (1058 KB) | HTML Full-text | XML Full-text
Abstract
To prepare a low-formaldehyde soy-based adhesive with good water resistance, phenol-formaldehyde modified with glutaraldehyde (PFG) with lower free phenol and free formaldehyde contents was used to cross-link the soy-based adhesive. The results showed that the mechanical properties and water resistance of plywood prepared
[...] Read more.
To prepare a low-formaldehyde soy-based adhesive with good water resistance, phenol-formaldehyde modified with glutaraldehyde (PFG) with lower free phenol and free formaldehyde contents was used to cross-link the soy-based adhesive. The results showed that the mechanical properties and water resistance of plywood prepared with soy-based adhesive with PFG was better than that of plywood with the same amount of phenol-formaldehyde (PF). The reaction between phenol and glutaraldehyde was proved by 13C-NMR. Under the optimized preparation conditions for plywood, that is to say, press temperature 160 °C, press time 4 min and resin loading 320 g·m−2, type I plywood could be prepared with 9% PFG as a cross-linker of soy-based adhesive. The Differential Scanning Calorimetry (DSC) result confirmed the cross-linking reaction between soy-based adhesive and PFG or PF. The activation energy of soy-based adhesive with cross-linker PFG was higher than that with PF resin. Full article
(This article belongs to the collection Polymeric Adhesives)
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Open AccessArticle 5000 h Multi-Factor Accelerated Aging Test of FRP Made Transmission Tower: Characterization, Thermal Decomposition and Reaction Kinetics Study
Polymers 2017, 9(5), 170; doi:10.3390/polym9050170
Received: 20 March 2017 / Revised: 3 May 2017 / Accepted: 6 May 2017 / Published: 10 May 2017
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Abstract
Three kinds of fiber reinforced plastic (FRP) composites, including modified polyurethane resin (LGD), epoxy resin (E44) and modified unsaturated polyester resin (D33) glass-fiber reinforced plastics, were subjected to a 5000 h multi-factor accelerated aging test according to the power industry standard. To examine
[...] Read more.
Three kinds of fiber reinforced plastic (FRP) composites, including modified polyurethane resin (LGD), epoxy resin (E44) and modified unsaturated polyester resin (D33) glass-fiber reinforced plastics, were subjected to a 5000 h multi-factor accelerated aging test according to the power industry standard. To examine aging resistance and thermal stability of transmission towers made by these three composites, relevant bending properties, thermogravimetric analysis (TGA) and derivative thermogravimetry (DTG), activation energy, as well as microscopic morphology were revealed. The results showed that for these composites, bending modulus retention rates were higher than 94% under the aging test and that of the LGD was highest. Additionally, the onset degradation temperature, temperature at maximum rate of weight loss and T5% reduced at 5000 h, with D33 having highest value and lowest decline rate. The activation energy was calculated with the Bagchi, Coats-Redfern and Broido method, respectively. Although the activation energy of all composites decreased after test, the D33, LGD materials had the highest activation energy which enjoys slight decline. Analysis of the whole experimental results suggested that D33 and LGD composites have good aging resistance, whose basic performance could still perform well after 5000 h aging test, so they can be used to composite towers and applied to engineering practice. Full article
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Open AccessArticle Study on the Mechanism of a Side Coupling Reaction during the Living Anionic Copolymerization of Styrene and 1-(Ethoxydimethylsilyphenyl)-1-phenylethylene (DPE-SiOEt)
Polymers 2017, 9(5), 171; doi:10.3390/polym9050171
Received: 8 April 2017 / Revised: 24 April 2017 / Accepted: 8 May 2017 / Published: 11 May 2017
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Abstract
A 1,1-diphenylethylene (DPE) derivative with an alkoxysilyl group (DPE-SiOEt) was synthesized. It was end-capped with poly(styryl)lithium (PSLi) and then copolymerized with styrene via living anionic polymerization (LAP) in a non-polar solvent at room temperature. The observed side coupling reaction was carefully investigated by
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A 1,1-diphenylethylene (DPE) derivative with an alkoxysilyl group (DPE-SiOEt) was synthesized. It was end-capped with poly(styryl)lithium (PSLi) and then copolymerized with styrene via living anionic polymerization (LAP) in a non-polar solvent at room temperature. The observed side coupling reaction was carefully investigated by end-capping the polymer. Changes in molecular weight support the plausibility of a mechanism involving living anionic species (PSLi or lithiated DPE-end-capped polystyrene, PSDLi) and the alkoxysilyl groups. Through a series of copolymerizations with different feed ratios, the kinetics of the side coupling reaction were also studied. The results showed that the side reactions could be controlled using an excess feed of DPE-SiOEt, a potentially useful strategy for the synthesis and application of well-defined alkoxysilyl-functionalized polymers via LAP. Full article
(This article belongs to the Special Issue Living Polymerization)
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Open AccessArticle Synthesis of Well-Defined Poly(N-H Benzamide-co-N-Octyl Benzamide)s and the Study of their Blends with Nylon 6
Polymers 2017, 9(5), 172; doi:10.3390/polym9050172
Received: 9 March 2017 / Revised: 9 May 2017 / Accepted: 10 May 2017 / Published: 13 May 2017
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Abstract
We synthesized a series of copolybenzamides (PBA) through chain-growth condensation polymerization (CGCP) of 4-(octylamino)benzoate (M4OB) and methyl 3-(4-(octyloxy)benzylamino) benzoate (M3OOB) co-monomers. Well-defined copolybenzamides with close to theoretical molecular weights (Mn ≈ 10,000–13,000) and narrow molecular weight distributions (Mw/Mn < 1.40) were obtained. Selective
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We synthesized a series of copolybenzamides (PBA) through chain-growth condensation polymerization (CGCP) of 4-(octylamino)benzoate (M4OB) and methyl 3-(4-(octyloxy)benzylamino) benzoate (M3OOB) co-monomers. Well-defined copolybenzamides with close to theoretical molecular weights (Mn ≈ 10,000–13,000) and narrow molecular weight distributions (Mw/Mn < 1.40) were obtained. Selective removals of the protecting group (i.e., 4-(octyloxy)benzyl group) from the affording P(M3OOB-co-M4OB) copolybenzamides were subsequently performed to obtain P(M3NH-co-M4OB) copolymers. These novel N-H-containing copolybenzamides (named as PNHBA) can not only provide hydrogen bonds for polymer-polymer blends but also have good solubility in organic solvents. Miscibility of the PNHBA and Nylon 6 blends was investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), FT-IR, contact angle analysis, transmission electron microscope (TEM), and dynamic mechanical analysis (DMA). This study illustrates a novel type of copolybenzamide with controlled molecular weight and narrow molecular weight distribution through an effective synthetic strategy, and can be applied to a practical blend of Nylon 6 with good miscibility. Full article
(This article belongs to the Special Issue Polymer Blends 2017)
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Open AccessArticle Synthesis, Characterization and Application of Four Novel Electrochromic Materials Employing Nitrotriphenylamine Unit as the Acceptor and Different Thiophene Derivatives as the Donor
Polymers 2017, 9(5), 173; doi:10.3390/polym9050173
Received: 23 April 2017 / Revised: 9 May 2017 / Accepted: 10 May 2017 / Published: 13 May 2017
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Abstract
In this study, four novel donor–acceptor systems, 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin -5-yl)-N-(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)phenyl)-N-(4-nitrophenyl)aniline (NETPA), 4- (4-methoxythiophen-2-yl)-N-(4-(4-methoxythiophen-2-yl)phenyl)-N-(4-nitrophenyl)aniline (NMOTPA), 4-(4-methylthiophen-2-yl)-N-(4-(4-methylthiophen-2-yl)phenyl)-N-(4-nitrophenyl) aniline (NMTPA) and 4-nitro-N,N-bis(4-(thiophen-2-yl)phenyl)aniline (NTTPA), were successfully synthesized by Stille coupling reaction and electropolymerized to obtain highly stable conducting polymers, PNETPA, PNMOTPA, PNMTPA and PNTTPA, respectively. The polymers were
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In this study, four novel donor–acceptor systems, 4-(2,3-dihydrothieno[3,4-b][1,4]dioxin -5-yl)-N-(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)phenyl)-N-(4-nitrophenyl)aniline (NETPA), 4- (4-methoxythiophen-2-yl)-N-(4-(4-methoxythiophen-2-yl)phenyl)-N-(4-nitrophenyl)aniline (NMOTPA), 4-(4-methylthiophen-2-yl)-N-(4-(4-methylthiophen-2-yl)phenyl)-N-(4-nitrophenyl) aniline (NMTPA) and 4-nitro-N,N-bis(4-(thiophen-2-yl)phenyl)aniline (NTTPA), were successfully synthesized by Stille coupling reaction and electropolymerized to obtain highly stable conducting polymers, PNETPA, PNMOTPA, PNMTPA and PNTTPA, respectively. The polymers were characterized using cyclic voltammetry (CV), step profiling and UV–Vis–NIR spectroscopy. The band gaps (Eg values) were 1.34, 1.59, 2.26, and 2.34 eV, for PNETPA, PNMOTPA, PNMTPA and PNTTPA, respectively. In addition, electrochromic switching showed that all polymers exhibit outstanding optical contrasts, high coloration efficiencies and fast switching speeds in the near-infrared region (NIR). These properties make the polymers suitable materials for electrochromic applications in NIR region. Full article
(This article belongs to the Special Issue Conductive Polymers 2017)
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Open AccessArticle pH Dependence of Chitosan Enzymolysis
Polymers 2017, 9(5), 174; doi:10.3390/polym9050174
Received: 23 March 2017 / Revised: 5 May 2017 / Accepted: 11 May 2017 / Published: 13 May 2017
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Abstract
As a means of making chitosan more useful in biotechnological applications, it was hydrolyzed using pepsin, chitosanase and α-amylase. The enzymolysis behavior of these enzymes was further systematically studied for its effectiveness in the production of low-molecular-weight chitosans (LMWCs) and other derivatives. The
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As a means of making chitosan more useful in biotechnological applications, it was hydrolyzed using pepsin, chitosanase and α-amylase. The enzymolysis behavior of these enzymes was further systematically studied for its effectiveness in the production of low-molecular-weight chitosans (LMWCs) and other derivatives. The study showed that these enzymes depend on ion hydronium (H3O+), thus on pH with a pH dependence fitting R2 value of 0.99. In y = 1.484[H^+] + 0.114, the equation of pH dependence, when [H^+] increases by one, y (k_0/k_m) increases by 1.484. From the temperature dependence study, the activation energy (Ea) and pre-exponential factor (A) were almost identical for two of the enzymes, but a considerable difference was observed in comparison with the third enzyme. Chitosanase and pepsin had nearly identical Ea, but α-amylase was significantly lower. This serves as evidence that the hydrolysis reaction of α-amylase relies on low-barrier hydrogen bonds (LBHBs), which explains its low Ea in actual conditions. The confirmation of this phenomenon was further derived from a similarly considerable difference in the order magnitudes of A between α-amylase and the other two enzymes, which was more than five. Variation of the rate constants of the enzymatic hydrolysis of chitosan with temperature follows the Arrhenius equation. Full article
(This article belongs to the Special Issue Biodegradable Polymers)
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Open AccessArticle Calcium Silicate Improved Bioactivity and Mechanical Properties of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Scaffolds
Polymers 2017, 9(5), 175; doi:10.3390/polym9050175
Received: 2 April 2017 / Revised: 12 May 2017 / Accepted: 12 May 2017 / Published: 14 May 2017
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Abstract
The poor bioactivity and mechanical properties have restricted its biomedical application, although poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) had good biocompatibility and biodegradability. In this study, calcium silicate (CS) was incorporated into PHBV for improving its bioactivity and mechanical properties, and the porous PHBV/CS composite scaffolds were
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The poor bioactivity and mechanical properties have restricted its biomedical application, although poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) had good biocompatibility and biodegradability. In this study, calcium silicate (CS) was incorporated into PHBV for improving its bioactivity and mechanical properties, and the porous PHBV/CS composite scaffolds were fabricated via selective laser sintering (SLS). Simulated body fluid (SBF) immersion tests indicated the composite scaffolds had good apatite-forming ability, which could be mainly attributed to the electrostatic attraction of negatively charged silanol groups derived from CS degradation to positively charged calcium ions in SBF. Moreover, the compressive properties of the composite scaffolds increased at first, and then decreased with increasing the CS content, which was ascribed to the fact that CS of a proper content could homogeneously disperse in PHBV matrix, while excessive CS would form continuous phase. The compressive strength and modulus of composite scaffolds with optimal CS content of 10 wt % were 3.55 MPa and 36.54 MPa, respectively, which were increased by 41.43% and 28.61%, respectively, as compared with PHBV scaffolds. Additionally, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay indicated MG63 cells had a higher proliferation rate on PHBV/CS composite scaffolds than that on PHBV. Alkaline phosphatase (ALP) staining assay demonstrated the incorporation of CS significantly promoted osteogenic differentiation of MG63 cells on the scaffolds. These results suggest that the PHBV/CS composite scaffolds have the potential in serving as a substitute in bone tissue engineering. Full article
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Open AccessArticle Novel Wet Micro-Contact Deprinting Method for Patterning Gold Nanoparticles on PEG-Hydrogels and Thereby Controlling Cell Adhesion
Polymers 2017, 9(5), 176; doi:10.3390/polym9050176
Received: 4 April 2017 / Revised: 8 May 2017 / Accepted: 11 May 2017 / Published: 15 May 2017
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Abstract
In the present work we introduce a novel method to create linear and rectangular micro-patterns of gold nanoparticles (Au NPs) on poly(ethylene glycol) (PEG) hydrogels. The strategy consists of removing Au NPs from defined regions of the silicon wafer by virtue of the
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In the present work we introduce a novel method to create linear and rectangular micro-patterns of gold nanoparticles (Au NPs) on poly(ethylene glycol) (PEG) hydrogels. The strategy consists of removing Au NPs from defined regions of the silicon wafer by virtue of the swelling effect of the hydrogel. Using this method, which we denote as “Wet Micro-Contact Deprinting”, well-defined micro-patterns of Au NPs on silicon can be created. This resulting pattern is then transferred from the hard substrate to the soft surface of PEG-hydrogels. These unique micro- and nano-patterned hydrogels were cultured with mouse fibroblasts L929 cells. The cells selectively adhered on the Au NPs coated area and avoided the pure PEG material. These patterned, nanocomposite biointerfaces are not only useful for biological and biomedical applications, such as tissue engineering and diagnostics, but also, for biosensor applications taking advantage of surface plasmon resonance (SPR) or surface enhanced Raman scattering (SERS) effects, due to the optical properties of the Au NPs. Full article
(This article belongs to the Special Issue Bio-inspired and Bio-based Polymers)
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Open AccessArticle Evaluation of Amphiphilic Peptide Modified Antisense Morpholino Oligonucleotides In Vitro and in Dystrophic mdx Mice
Polymers 2017, 9(5), 177; doi:10.3390/polym9050177
Received: 21 March 2017 / Revised: 28 April 2017 / Accepted: 8 May 2017 / Published: 15 May 2017
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Abstract
A series of amphiphilic peptides modified PMO (Pt-PMO) were prepared, and their antisense effect and toxicity were evaluated both in vitro and in mdx mice. The results showed that the exon-skipping performance of Pt-PMO are relative to the structure of the conjugated peptide:
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A series of amphiphilic peptides modified PMO (Pt-PMO) were prepared, and their antisense effect and toxicity were evaluated both in vitro and in mdx mice. The results showed that the exon-skipping performance of Pt-PMO are relative to the structure of the conjugated peptide: the Pt3/Pt4 composed of six/seven arginines and one myristoylation modified PMO showed more efficacy and with less toxicity as compared to others, confirming that appropriate hydrophilic-lipophilic balance (HLB) and cationic sequence numbers play a crucial role in improving cell uptake and corresponding exon-skipping efficiency. This was observed particularly in enhanced delivery efficiency of PMO comparable to B-PMO in vitro, while 6-fold improved exon-skipping was achieved against naked PMO in vivo. The multi-PMO modified Pt8-PMO also showed improved exon-skipping both in vitro and in vivo, though there is lower efficiency in systemic delivery as compared to Pt4-PMO. These data suggest that with optimization of peptide in component, charge density has clear potential for exploration towards achieving higher efficiency of antisense oligonucleotide systemic delivery, and thus is more applicable for clinical application. Full article
(This article belongs to the Special Issue Polymers and Nanogels for Gene Therapy)
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Open AccessArticle Intensification of Electrochemical Performance of AA7075 Aluminum Alloys Using Rare Earth Functionalized Water-Based Polymer Coatings
Polymers 2017, 9(5), 178; doi:10.3390/polym9050178
Received: 21 March 2017 / Revised: 28 April 2017 / Accepted: 16 May 2017 / Published: 18 May 2017
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Abstract
This work reports the effect of different amounts of ceria nanoparticles on UV resistance and barrier properties of water-based polyurethane (WPU) on glass and AA7075 aluminum alloy substrates. Hybrid coatings were synthesized from an aliphatic WPU–HDI (1,6-hexamethylene di-isocyanate) and cerium oxide nanoparticles (CeO
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This work reports the effect of different amounts of ceria nanoparticles on UV resistance and barrier properties of water-based polyurethane (WPU) on glass and AA7075 aluminum alloy substrates. Hybrid coatings were synthesized from an aliphatic WPU–HDI (1,6-hexamethylene di-isocyanate) and cerium oxide nanoparticles (CeO2) with an average particle size distribution of about 25 nm. Different nanoceria amounts (1, 3 and 5 wt %), mixing times (30, 60 and 120 min) and methods to disperse the nanostructures into the polymer matrix (magnetic stirring and sonication) were evaluated. Initially, the dispersion of CeO2 nanoparticles embedded in the polymer matrix and displacement in the corrosion potential (Ecorr) were analyzed by confocal scanning laser microscopy (CLSM) and open circuit potential (Eocp) measurements. According to this behavior, the dispersion and water ratio required during the polymerization process were established. Coated samples obtained after the second stage were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical light microscopy. In addition, optical measurements on glass substrates were evaluated with UV-vis spectroscopy. The effect of the synthesis parameters on the corrosion behavior of WPU–CeO2/AA7075 systems was investigated with Eocp and electrochemical impedance spectroscopy (EIS) in a 3 wt % NaCl solution. In addition, the films were subjected to 180 h of accelerated weathering. The results show that the combination of specific nanoceria addition with the optimal synthesis parameters enhances optical transparence of WPU as well as barrier properties. From these, the coated specimens prepared with 3 wt % of ceria content and sonicated for 30 min showed a highly dispersed system, which results in a high charge transfer resistance. The observed properties in clear coats deposited on metallic substrates suggested an improvement in the appearance and less deterioration in UV exposure in comparison with pure WPU, enhancing the protective properties of the AA7075 aluminum alloy when exposed to a corrosive medium. Full article
(This article belongs to the Special Issue Polymer Nanocomposites)
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Open AccessArticle In Situ Self-Assembled Nanocomposites from Bacterial Cellulose Reinforced with Eletrospun Poly(lactic acid)/Lipids Nanofibers
Polymers 2017, 9(5), 179; doi:10.3390/polym9050179
Received: 16 April 2017 / Revised: 12 May 2017 / Accepted: 14 May 2017 / Published: 19 May 2017
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Abstract
The goal of this study is to explore a new strategy to improve the mechanical and hydrophobic properties of bacterial cellulose (BC) mats. The present work is the first to report the preparation of in situ self-assembled BC nanocomposites using electrospun hydrophobic poly(lactic
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The goal of this study is to explore a new strategy to improve the mechanical and hydrophobic properties of bacterial cellulose (BC) mats. The present work is the first to report the preparation of in situ self-assembled BC nanocomposites using electrospun hydrophobic poly(lactic acid) (PLA) or PLA/lipids (PLA/Lip) nanofiber mats as foundation for BC nanofiber growth. Adding electrospun PLA mats to the BC culture media led to a two-fold increase in toughness with a 52% increase in elongation of the nanocomposites with regard to BC. The incorporation of electrospun PLA and PLA/Lip nanofiber mats lowered the moisture regain and water vapor transmission of BC nanocomposites relative to pure BC mats. The interfacial bonding between the individual components of a nanocomposite is a key factor for the improvement of composite strength, stiffness, and barrier properties; thus additional strategies to improve interaction between hydrophilic BC and hydrophobic PLA fibers need to be explored. Full article
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Open AccessArticle Glass Fiber Reinforced Polymer (GFRP) Bars for Enhancing the Flexural Performance of RC Beams Using Side-NSM Technique
Polymers 2017, 9(5), 180; doi:10.3390/polym9050180
Received: 1 April 2017 / Revised: 16 May 2017 / Accepted: 17 May 2017 / Published: 19 May 2017
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Abstract
Reinforced concrete (RC) structures require strengthening for numerous factors, such as increased load, modification of the structural systems, structural upgrade or errors in the design and construction stages. The side near-surface mounted (SNSM) strengthening technique with glass fiber-reinforced polymer (GFRP) bars is a
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Reinforced concrete (RC) structures require strengthening for numerous factors, such as increased load, modification of the structural systems, structural upgrade or errors in the design and construction stages. The side near-surface mounted (SNSM) strengthening technique with glass fiber-reinforced polymer (GFRP) bars is a relatively new emerging technique for enhancing the flexural capacities of existing RC elements. Nine RC rectangular beams were flexurally strengthened with this technique and tested under four-point bending loads until failure. The main goal of this study is to optimize the structural capacity of the RC beams by varying the amount of strengthening reinforcement and bond length. The experimental test results showed that strengthening with SNSM GFRP bars significantly enhanced the flexural responses of the specimens compared with the control specimen. The first cracking and ultimate loads, energy absorption capacities, ductility and stiffness were remarkably enhanced by the SNSM technique. It was also confirmed that the bond length of the strengthened reinforcement greatly influences the energy absorption capacities, ductility and stiffness. The effect of the bond length on these properties is more significant compared to the amount of strengthening reinforcement. Full article
(This article belongs to the Special Issue Functionally Responsive Polymeric Materials)
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Open AccessArticle Synthesis and Study of Shape-Memory Polymers Selectively Induced by Near-Infrared Lights via In Situ Copolymerization
Polymers 2017, 9(5), 181; doi:10.3390/polym9050181
Received: 16 April 2017 / Revised: 16 May 2017 / Accepted: 17 May 2017 / Published: 20 May 2017
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Abstract
Shape-memory polymers (SMPs) selectively induced by near-infrared lights of 980 or 808 nm were synthesized via free radical copolymerization. Methyl methacrylate (MMA) monomer, ethylene glycol dimethylacrylate (EGDMA) as a cross-linker, and organic complexes of Yb(TTA)2AAPhen or Nd(TTA)2AAPhen containing a reactive ligand of acrylic
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Shape-memory polymers (SMPs) selectively induced by near-infrared lights of 980 or 808 nm were synthesized via free radical copolymerization. Methyl methacrylate (MMA) monomer, ethylene glycol dimethylacrylate (EGDMA) as a cross-linker, and organic complexes of Yb(TTA)2AAPhen or Nd(TTA)2AAPhen containing a reactive ligand of acrylic acid (AA) were copolymerized in situ. The dispersion of the organic complexes in the copolymer matrix was highly improved, while the transparency of the copolymers was negligibly influenced in comparison with the pristine cross-linked PMMA. In addition, the thermal resistance of the copolymers was enhanced with the complex loading, while their glass transition temperature, cross-linking level, and mechanical properties were to some extent reduced. Yb(TTA)2AAPhen and Nd(TTA)2AAPhen provided the prepared copolymers with selective photothermal effects and shape-memory functions for 980 and 808 nm NIR lights, respectively. Finally, smart optical devices which exhibited localized transparency or diffraction evolution procedures were demonstrated based on the prepared copolymers, owing to the combination of good transparency and selective light wavelength responsivity. Full article
(This article belongs to the Special Issue Functionally Responsive Polymeric Materials)
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Open AccessArticle Osteochondral Regeneration Induced by TGF-β Loaded Photo Cross-Linked Hyaluronic Acid Hydrogel Infiltrated in Fused Deposition-Manufactured Composite Scaffold of Hydroxyapatite and Poly (Ethylene Glycol)-Block-Poly(ε-Caprolactone)
Polymers 2017, 9(5), 182; doi:10.3390/polym9050182
Received: 6 March 2017 / Revised: 11 May 2017 / Accepted: 14 May 2017 / Published: 20 May 2017
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Abstract
The aim of this study was to report the fabrication of porous scaffolds with pre-designed internal pores using a fused deposition modeling (FDM) method. Polycaprolactone (PCL) is a suitable material for the FDM method due to the fact it can be melted and
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The aim of this study was to report the fabrication of porous scaffolds with pre-designed internal pores using a fused deposition modeling (FDM) method. Polycaprolactone (PCL) is a suitable material for the FDM method due to the fact it can be melted and has adequate flexural modulus and strength to be formed into a filament. In our study, the filaments of methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) having terminal groups of carboxylic acid were deposited layer by layer. Raw materials having a weight ratio of hydroxyapatite (HAp) to polymer of 1:2 was used for FDM. To promote cell adhesion, amino groups of the Arg-Gly-Asp(RGD) peptide were condensed with the carboxylic groups on the surface of the fabricated scaffold. Then the scaffold was infiltrated with hydrogel of glycidyl methacrylate hyaluronic acid loading with 10 ng/mL of TGF-β1 and photo cross-linked on the top of the scaffolds. Serious tests of mechanical and biological properties were performed in vitro. HAp was found to significantly increase the compressive strength of the porous scaffolds. Among three orientations of the filaments, the lay down pattern 0°/90° scaffolds exhibited the highest compressive strength. Fluorescent staining of the cytoskeleton found that the osteoblast-like cells and stem cells well spread on RGD-modified PEG-PCL film indicating a favorable surface for the proliferation of cells. An in vivo test was performed on rabbit knee. The histological sections indicated that the bone and cartilage defects produced in the knees were fully healed 12 weeks after the implantation of the TGF-β1 loaded hydrogel and scaffolds, and regenerated cartilage was hyaline cartilage as indicated by alcian blue and periodic acid-schiff double staining. Full article
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Open AccessArticle Electrospun Polycaprolactone/Aloe Vera_Chitosan Nanofibrous Asymmetric Membranes Aimed for Wound Healing Applications
Polymers 2017, 9(5), 183; doi:10.3390/polym9050183
Received: 3 April 2017 / Revised: 6 May 2017 / Accepted: 19 May 2017 / Published: 21 May 2017
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Abstract
Today, none of the wound dressings available on the market is fully capable of reproducing all the features of native skin. Herein, an asymmetric electrospun membrane was produced to mimic both layers of skin. It comprises a top dense layer (manufactured with polycaprolactone)
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Today, none of the wound dressings available on the market is fully capable of reproducing all the features of native skin. Herein, an asymmetric electrospun membrane was produced to mimic both layers of skin. It comprises a top dense layer (manufactured with polycaprolactone) that was designed to provide mechanical support to the wound and a bottom porous layer (composed of chitosan and Aloe Vera) aimed to improve the bactericidal activity of the membrane and ultimately the healing process. The results obtained revealed that the produced asymmetric membranes displayed a porosity, wettability, as well as mechanical properties similar to those presented by the native skin. Fibroblast cells were able to adhere, spread, and proliferate on the surface of the membranes and the intrinsic structure of the two layers of the membrane is capable of avoiding the invasion of microorganisms while conferring bioactive properties. Such data reveals the potential of these asymmetric membranes, in the near future, to be applied as wound dressings. Full article
(This article belongs to the Special Issue Advance of Polymers Applied to Biomedical Applications: Biointerface)
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Open AccessArticle Investigation on the Influence of Chain Extenders on the Performance of One-Component Moisture-Curable Polyurethane Adhesives
Polymers 2017, 9(5), 184; doi:10.3390/polym9050184
Received: 2 April 2017 / Revised: 15 May 2017 / Accepted: 16 May 2017 / Published: 21 May 2017
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Abstract
In this work, a number of chain extended moisture-curable urethane prepolymers were synthesized in order to develop isocyanate terminated urethane prepolymer formulations that would simultaneously display both high adhesive strength and low viscosity. Proton nuclear magnetic resonance spectroscopy (1H-NMR), size exclusion
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In this work, a number of chain extended moisture-curable urethane prepolymers were synthesized in order to develop isocyanate terminated urethane prepolymer formulations that would simultaneously display both high adhesive strength and low viscosity. Proton nuclear magnetic resonance spectroscopy (1H-NMR), size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and Brookfield viscometry were utilized for characterizing the prepared urethane prepolymers. In addition, the adhesion strength of the cured prepolymers was determined by tensile shear strength test according to the DIN EN (Deutsches Institut für Normung, the German Institute for Standardization) 1465 standard. Especially, the role of different types of linear (butanediol, pentanediol) and branched chain extenders (dipropyleneglycol (di-PPG), tripropyleneglycol (tri-PPG) and the influence of their dosage on the degree of microphase separation between hard segments (HS) and soft segments (SS) in urethane prepolymers were studied. Furthermore, the benefits of utilizing either a one-step versus a two-step polymerization process were investigated. The results revealed that the extent of phase separation of different urethane prepolymers was dependent on the extent of hydrogen bonding interactions which was extensively studied by attenuated total reflectance infrared spectroscopy (ATR-FTIR). The incorporation of branched chain extenders (di-PPG and tri-PPG) did not result in notable phase separation between hard segments and soft segments, while linear chain extenders (pentanediol and butanediol) readily promoted phase separation. The degree of phase separation was particularly pronounced for butanediol, and when the linear chain extender ratio was higher than or equal to 0.74. Compared with a two-stage process, one-stage process produced more randomly distributed polymer chains with highly dispersed hard segments. Thus, urethane prepolymers exhibiting strong adhesive strength with simultaneously low viscosity were successfully developed by systematic adjustment of structural parameters. Full article
(This article belongs to the collection Polymeric Adhesives)
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Open AccessReview Chemo-Electrical Gas Sensors Based on Conducting Polymer Hybrids
Polymers 2017, 9(5), 155; doi:10.3390/polym9050155
Received: 10 March 2017 / Revised: 24 April 2017 / Accepted: 24 April 2017 / Published: 26 April 2017
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Abstract
Conducting polymer (CP) hybrids, which combine CPs with heterogeneous species, have shown strong potential as electrical transducers in chemosensors. The charge transport properties of CPs are based on chemical redox reactions and provide various chemo-electrical signal transduction mechanisms. Combining CPs with other functional
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Conducting polymer (CP) hybrids, which combine CPs with heterogeneous species, have shown strong potential as electrical transducers in chemosensors. The charge transport properties of CPs are based on chemical redox reactions and provide various chemo-electrical signal transduction mechanisms. Combining CPs with other functional materials has provided opportunities to tailor their major morphological and physicochemical properties, often resulting in enhanced sensing performance. The hybrids can provide an enlarged effective surface area for enhanced interaction and chemical specificity to target analytes via a new signal transduction mechanism. Here, we review a selection of important CPs, including polyaniline, polypyrrole, polythiophene and their derivatives, to fabricate versatile organic and inorganic hybrid materials and their chemo-electrical sensing performance. We focus on what benefits can be achieved through material hybridization in the sensing application. Moreover, state-of-the-art trends in technologies of CP hybrid sensors are discussed, as are limitations and challenges. Full article
(This article belongs to the Special Issue Polymers for Chemosensing)
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Open AccessReview Biomedical and Microbiological Applications of Bio-Based Porous Materials: A Review
Polymers 2017, 9(5), 160; doi:10.3390/polym9050160
Received: 31 January 2017 / Revised: 15 April 2017 / Accepted: 25 April 2017 / Published: 29 April 2017
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Abstract
Extensive employment of biomaterials in the areas of biomedical and microbiological applications is considered to be of prime importance. As expected, oil based polymer materials were gradually replaced by natural or synthetic biopolymers due to their well-known intrinsic characteristics such as biodegradability, non-toxicity
[...] Read more.
Extensive employment of biomaterials in the areas of biomedical and microbiological applications is considered to be of prime importance. As expected, oil based polymer materials were gradually replaced by natural or synthetic biopolymers due to their well-known intrinsic characteristics such as biodegradability, non-toxicity and biocompatibility. Literature on this subject was found to be expanding, especially in the areas of biomedical and microbiological applications. Introduction of porosity into a biomaterial broadens the scope of applications. In addition, increased porosity can have a beneficial effect for the applications which exploit their exceptional ability of loading, retaining and releasing of fluids. Different applications require a unique set of pore characteristics in the biopolymer matrix. Various pore morphologies have different characteristics and contribute different performances to the biopolymer matrix. Fabrication methods for bio-based porous materials more related to the choice of material. By choosing the appropriate combination of fabrication technique and biomaterial employment, one can obtain tunable pore characteristic to fulfill the requirements of desired application. In our previous review, we described the literature related to biopolymers and fabrication techniques of porous materials. This paper we will focus on the biomedical and microbiological applications of bio-based porous materials. Full article
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