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Polymers, Volume 6, Issue 9 (September 2014), Pages 2309-2509

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Research

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Open AccessArticle Preparation and Characterization of ZnS, CdS and HgS/Poly(methyl methacrylate) Nanocomposites
Polymers 2014, 6(9), 2332-2344; doi:10.3390/polym6092332
Received: 26 May 2014 / Revised: 24 July 2014 / Accepted: 4 August 2014 / Published: 5 September 2014
Cited by 5 | PDF Full-text (3704 KB) | HTML Full-text | XML Full-text
Abstract
The synthesis and characterization of ZnS/PMMA (poly(methyl methacrylate)), CdS/PMMA and HgS/PMMA nanocomposites are presented. Hexadecylamine (HDA)-capped ZnS, CdS and HgS nanoparticles were synthesized using dithiocarbamate single molecule precursors at 180 °C. FTIR (Fourier transform infrared spectroscopy) spectra measurement confirmed the dispersion of [...] Read more.
The synthesis and characterization of ZnS/PMMA (poly(methyl methacrylate)), CdS/PMMA and HgS/PMMA nanocomposites are presented. Hexadecylamine (HDA)-capped ZnS, CdS and HgS nanoparticles were synthesized using dithiocarbamate single molecule precursors at 180 °C. FTIR (Fourier transform infrared spectroscopy) spectra measurement confirmed the dispersion of the metal sulfide nanoparticles in the PMMA matrices to form the metal sulfides/PMMA nanocomposites. Powder X-ray diffraction confirmed the presence of the amorphous PMMA in the nanocomposites. The ZnS and HgS particles were indexed to the cubic phase, while the HgS particles correspond to the hexagonal phase. Thermogravimetric analyses showed that the metal sulfide nanocomposites are thermally more stable than their corresponding precursor complexes. The TEM (Transmission electron microscope) analyses revealed that the ZnS nanoparticles have a particle size of 3–5 nm; the crystallite size of the CdS nanoparticles is 6–12 nm, and HgS nanoparticles are 6–12 nm. Full article
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Open AccessCommunication Influence of Surface Treatment on Tensile Properties of Low-Density Polyethylene/Cellulose Woven Biocomposites: A Preliminary Study
Polymers 2014, 6(9), 2345-2356; doi:10.3390/polym6092345
Received: 5 June 2014 / Revised: 9 August 2014 / Accepted: 3 September 2014 / Published: 12 September 2014
Cited by 2 | PDF Full-text (7275 KB) | HTML Full-text | XML Full-text
Abstract
Cellulose woven (CW) was surface treated by means of hexadecyltrimethylammonium bromide surfactant (HTAB) in aqueous solution medium at elevated temperature. The parameters of the surface treatment that have been studied are HTAB concentration (0.2, 0.4, 0.6, 0.8 and 1.0 wt%) and treatment [...] Read more.
Cellulose woven (CW) was surface treated by means of hexadecyltrimethylammonium bromide surfactant (HTAB) in aqueous solution medium at elevated temperature. The parameters of the surface treatment that have been studied are HTAB concentration (0.2, 0.4, 0.6, 0.8 and 1.0 wt%) and treatment time (1, 2, 3, 4 and 5 h). The untreated and treated CW filled low-density polyethylene (LDPE) biocomposites were prepared via compression molding technique. The tensile testing results of LDPE/CW biocomposites demonstrated that the optimum HTAB concentration for treatment of CW in 1 h was 0.4 wt%, while the optimum treatment time at 0.4 wt% HTAB was 2 h. The SEM (scanning electron microscope) images indicated that there is no significant difference in the morphology of the untreated and treated CW; however the morphology of the LDPE/treated CW biocomposite showed better interfacial adhesion as compared with the untreated ones. The FTIR (Fourier transform infrared spectroscopy) spectra revealed that the presence of HTAB on the surface of treated CW and also revealed the existence of intermolecular interactions between LDPE and treated CW. In summary, HTAB could potentially be used as a treatment agent for modifying the surface of CW and consequently improved the tensile properties of LDPE/CW biocomposites. Full article
(This article belongs to the Special Issue Natural Polymers 2014)
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Open AccessArticle Laccase Immobilization by Chelated Metal Ion Coordination Chemistry
Polymers 2014, 6(9), 2357-2370; doi:10.3390/polym6092357
Received: 4 May 2014 / Revised: 28 July 2014 / Accepted: 26 August 2014 / Published: 15 September 2014
Cited by 2 | PDF Full-text (3001 KB) | HTML Full-text | XML Full-text
Abstract
In this work, amidoxime polyacrylonitrile (AOPAN) nanofibrous membrane was prepared by a reaction between PAN nanofibers and hydroxylamine hydrochloride. The AOPAN nanofibrous membranes were used for four metal ions (Fe3+, Cu2+, Ni2+, Cd2+) chelation [...] Read more.
In this work, amidoxime polyacrylonitrile (AOPAN) nanofibrous membrane was prepared by a reaction between PAN nanofibers and hydroxylamine hydrochloride. The AOPAN nanofibrous membranes were used for four metal ions (Fe3+, Cu2+, Ni2+, Cd2+) chelation under different conditions. Further, the competition of different metal ions coordinating with AOPAN nanofibrous membrane was also studied. The AOPAN chelated with individual metal ion (Fe3+, Cu2+, Ni2+, Cd2+) and also the four mixed metal ions were further used for laccase (Lac) immobilization. Compared with free laccase, the immobilized laccase showed better resistance to pH and temperature changes as well as improved storage stability. Among the four individual metal ion chelated membranes, the stability of the immobilized enzymes generally followed the order as Fe–AOPAN–Lac > Cu–AOPAN–Lac > Ni–AOPAN–Lac > Cd–AOPAN–Lac. In addition, the immobilized enzyme on the carrier of AOPAN chelated with four mixed metal ions showed the best properties. Full article
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Open AccessArticle Biopolymer Electrolyte Based on Derivatives of Cellulose from Kenaf Bast Fiber
Polymers 2014, 6(9), 2371-2385; doi:10.3390/polym6092371
Received: 23 June 2014 / Revised: 20 August 2014 / Accepted: 10 September 2014 / Published: 19 September 2014
Cited by 11 | PDF Full-text (683 KB) | HTML Full-text | XML Full-text
Abstract
A cellulose derivative, carboxymethyl cellulose (CMC), was synthesized by the reaction of cellulose from kenaf bast fiber with monochloroacetic acid. A series of biopolymer electrolytes comprised of the synthesized CMC and ammonium acetate (CH3COONH4) were prepared by the [...] Read more.
A cellulose derivative, carboxymethyl cellulose (CMC), was synthesized by the reaction of cellulose from kenaf bast fiber with monochloroacetic acid. A series of biopolymer electrolytes comprised of the synthesized CMC and ammonium acetate (CH3COONH4) were prepared by the solution-casting technique. The biopolymer-based electrolyte films were characterized by Fourier Transform Infrared spectroscopy to investigate the formation of the CMC–CH3COONH4 complexes. Electrochemical impedance spectroscopy was conducted to obtain their ionic conductivities. The highest conductivity at ambient temperature of 5.77 × 10−4 S cm−1 was obtained for the electrolyte film containing 20 wt% of CH3COONH4. The biopolymer electrolyte film also exhibited electrochemical stability up to 2.5 V. These results indicated that the biopolymer electrolyte has great potential for applications to electrochemical devices, such as proton batteries and solar cells. Full article
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Open AccessArticle Barrier Properties of Polylactic Acid in Cellulose Based Packages Using Montmorillonite as Filler
Polymers 2014, 6(9), 2386-2403; doi:10.3390/polym6092386
Received: 7 July 2014 / Revised: 20 August 2014 / Accepted: 2 September 2014 / Published: 19 September 2014
Cited by 6 | PDF Full-text (1448 KB) | HTML Full-text | XML Full-text
Abstract
Polylactic acid (PLA) and montmorillonite (CB) as filler were studied as coatings for cellulose based packages. Amorphous (AM) and semi crystalline (SC) PLA were used at different concentrations according to a 2 × 6 × 3 full factorial experimental design. CB loading [...] Read more.
Polylactic acid (PLA) and montmorillonite (CB) as filler were studied as coatings for cellulose based packages. Amorphous (AM) and semi crystalline (SC) PLA were used at different concentrations according to a 2 × 6 × 3 full factorial experimental design. CB loading was three concentrations and coating was performed by casting. Contact angle (CA), water vapor (WVP) and grease permeabilities were measured for each resultant package and were compared to commercial materials (Glassine Paper, Grease Proof Papers 1 and 2 produced commercially). Significant differences were found and the main factors were the type and concentration of PLA. The best values were: for grease penetration, +1800 s; WVP from 161.36 to 237.8 g·µm·kPa−1·m−2·d−1 and CA from 69° to 73° for PLA–AM 0.5% and CB variable. These parameters are comparable to commercial packages used in the food industry. DSC revealed three different thermal events for PLA–SC and just Tg for PLA–AM. Crystallinity was also verified, obtaining a ΔHcrys of 3.7 J·g−1 for PLA–SC and 14 J·g−1 for PLA–SC–BC, evidencing clay interaction as a crystal nucleating agent. Differences found were explained on terms of the properties measured, where structural and chemical arrays of the coatings play a fundamental role for the barrier properties. Full article
(This article belongs to the Special Issue Packaging Films)
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Open AccessArticle Structural, Optical and Electrical Properties of PVA/PANI/Nickel Nanocomposites Synthesized by Gamma Radiolytic Method
Polymers 2014, 6(9), 2435-2450; doi:10.3390/polym6092435
Received: 21 February 2014 / Revised: 2 June 2014 / Accepted: 21 July 2014 / Published: 24 September 2014
Cited by 5 | PDF Full-text (2000 KB) | HTML Full-text | XML Full-text
Abstract
This article reports a simultaneous synthesis of polyaniline (PANI) and nickel (Ni) nanoparticles embedded in polyvinyl alcohol (PVA) film matrix by gamma radiolytic method. The mechanism of formation of PANI and Ni nanoparticles were proposed via oxidation of aniline and reduction of [...] Read more.
This article reports a simultaneous synthesis of polyaniline (PANI) and nickel (Ni) nanoparticles embedded in polyvinyl alcohol (PVA) film matrix by gamma radiolytic method. The mechanism of formation of PANI and Ni nanoparticles were proposed via oxidation of aniline and reduction of Ni ions, respectively. The effects of dose and Ni ions concentration on structural, optical, and electrical properties of the final PVA/PANI/Ni nanocomposites film were carefully examined. The structural and morphological studies show the presence of PANI with irregular granular microstructure and Ni nanoparticles with spherical shape and diameter less than 60 nm. The average particle size of Ni nanoparticles decreased with increasing dose and decreasing of precursor concentration due to increase of nucleation process over aggregation process during gamma irradiation. The optical absorption spectra showed that the absorption peak of Ni nanoparticles at about 390 nm shifted to lower wavelength and the absorbance increased with increasing dose. The formation of PANI was also revealed at 730 nm absorption peak with the absorbance increasing by the increase of dose. The electrical conductivity increased with increasing of dose and chlorine concentration due to number of polarons formation increases in the PVA/PANI/Ni nanocomposites. Full article
Open AccessArticle Polyplex Formation Influences Release Mechanism of Mono- and Di-Valent Ions from Phosphorylcholine Group Bearing Hydrogels
Polymers 2014, 6(9), 2451-2472; doi:10.3390/polym6092451
Received: 14 July 2014 / Revised: 3 September 2014 / Accepted: 9 September 2014 / Published: 25 September 2014
Cited by 3 | PDF Full-text (1905 KB) | HTML Full-text | XML Full-text
Abstract
The release of monovalent potassium and divalent calcium ions from zwitterionic phosphorylcholine containing poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogels was studied and the effects of polymer swelling, ion valence and temperature were investigated. For comparison, ions were loaded during hydrogel formulation or loaded by [...] Read more.
The release of monovalent potassium and divalent calcium ions from zwitterionic phosphorylcholine containing poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogels was studied and the effects of polymer swelling, ion valence and temperature were investigated. For comparison, ions were loaded during hydrogel formulation or loaded by partitioning following construct synthesis. Using the Koshmeyer-Peppas release model, the apparent diffusion coefficient, Dapp, and diffusional exponents, n, were Dapp (pre-K+) = 2.03 × 105, n = 0.4 and Dapp (post-K+) = 1.86 × 105, n = 0.33 respectively, indicative of Fickian transport. The Dapp (pre-Ca2+) = 3.90 × 106, n = 0.60 and Dapp (post-Ca2+) = 2.85 × 106, n = 0.85, respectively, indicative of case II and anomalous transport. Results indicate that divalent cations form cation-polyelectrolyte anion polymer complexes while monovalent ions do not. Temperature dependence of potassium ion release was shown to follow an Arrhenius-type relation with negative apparent activation energy of −19 ± 15 while calcium ion release was temperature independent over the physiologically relevant range (25–45 °C) studied. The negative apparent activation energy may be due to temperature dependent polymer swelling. No effect of polymer swelling on the diffusional exponent or rate constant was found suggesting polymer relaxation occurs independent of polymer swelling. Full article
(This article belongs to the Special Issue Complex Macromolecular Architectures)
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Review

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Open AccessReview A Survey of Surface Modification Techniques for Next-Generation Shape Memory Polymer Stent Devices
Polymers 2014, 6(9), 2309-2331; doi:10.3390/polym6092309
Received: 30 June 2014 / Revised: 12 August 2014 / Accepted: 19 August 2014 / Published: 29 August 2014
Cited by 6 | PDF Full-text (1386 KB) | HTML Full-text | XML Full-text
Abstract
The search for a single material with ideal surface properties and necessary mechanical properties is on-going, especially with regard to cardiovascular stent materials. Since the majority of stent problems arise from surface issues rather than bulk material deficiencies, surface optimization of a [...] Read more.
The search for a single material with ideal surface properties and necessary mechanical properties is on-going, especially with regard to cardiovascular stent materials. Since the majority of stent problems arise from surface issues rather than bulk material deficiencies, surface optimization of a material that already contains the necessary bulk properties is an active area of research. Polymers can be surface-modified using a variety of methods to increase hemocompatibilty by reducing either late-stage restenosis or acute thrombogenicity, or both. These modification methods can be extended to shape memory polymers (SMPs), in an effort to make these materials more surface compatible, based on the application. This review focuses on the role of surface modification of materials, mainly polymers, to improve the hemocompatibility of stent materials; additional discussion of other materials commonly used in stents is also provided. Although shape memory polymers are not yet extensively used for stents, they offer numerous benefits that may make them good candidates for next-generation stents. Surface modification techniques discussed here include roughening, patterning, chemical modification, and surface modification for biomolecule and drug delivery. Full article
(This article belongs to the Special Issue Shape-Memory Polymers)
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Open AccessReview Atomistic Studies of Mechanical Properties of Graphene
Polymers 2014, 6(9), 2404-2432; doi:10.3390/polym6092404
Received: 30 June 2014 / Revised: 4 September 2014 / Accepted: 5 September 2014 / Published: 22 September 2014
Cited by 24 | PDF Full-text (1108 KB) | HTML Full-text | XML Full-text
Abstract
Recent progress of simulations/modeling at the atomic level has led to a better understanding of the mechanical behaviors of graphene, which include the linear elastic modulus E, the nonlinear elastic modulus D, the Poisson’s ratio ν, the intrinsic strength [...] Read more.
Recent progress of simulations/modeling at the atomic level has led to a better understanding of the mechanical behaviors of graphene, which include the linear elastic modulus E, the nonlinear elastic modulus D, the Poisson’s ratio ν, the intrinsic strength σint and the corresponding strain εint as well as the ultimate strain εmax (the fracture strain beyond which the graphene lattice will be unstable). Due to the two-dimensional geometric characteristic, the in-plane tensile response and the free-standing indentation response of graphene are the focal points in this review. The studies are based on multiscale levels: including quantum mechanical and classical molecular dynamics simulations, and parallel continuum models. The numerical studies offer useful links between scientific research with engineering application, which may help to fulfill graphene potential applications such as nano sensors, nanotransistors, and other nanodevices. Full article
(This article belongs to the Special Issue Computational Chemistry)
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Open AccessReview Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics
Polymers 2014, 6(9), 2473-2509; doi:10.3390/polym6092473
Received: 28 July 2014 / Revised: 16 September 2014 / Accepted: 19 September 2014 / Published: 25 September 2014
Cited by 29 | PDF Full-text (5624 KB) | HTML Full-text | XML Full-text
Abstract
Organic photovoltaic cells (OPVs) have been a hot topic for research during the last decade due to their promising application in relieving energy pressure and environmental problems caused by the increasing combustion of fossil fuels. Much effort has been made toward understanding [...] Read more.
Organic photovoltaic cells (OPVs) have been a hot topic for research during the last decade due to their promising application in relieving energy pressure and environmental problems caused by the increasing combustion of fossil fuels. Much effort has been made toward understanding the photovoltaic mechanism, including evolving chemical structural motifs and designing device structures, leading to a remarkable enhancement of the power conversion efficiency of OPVs from 3% to over 15%. In this brief review, the advanced progress and the state-of-the-art performance of OPVs in very recent years are summarized. Based on several of the latest developed approaches to accurately detect the separation of electron-hole pairs in the femtosecond regime, the theoretical interpretation to exploit the comprehensive mechanistic picture of energy harvesting and charge carrier generation are discussed, especially for OPVs with bulk and multiple heterojunctions. Subsequently, the novel structural designs of the device architecture of OPVs embracing external geometry modification and intrinsic structure decoration are presented. Additionally, some approaches to further increase the efficiency of OPVs are described, including thermotics and dynamics modification methods. Finally, this review highlights the challenges and prospects with the aim of providing a better understanding towards highly efficient OPVs. Full article
(This article belongs to the Special Issue Organic Solar Cells)
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Other

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Open AccessCorrection Correction: Guo, Q.; et al. Comparison of in Situ and ex Situ Methods for Synthesis of Two-Photon Polymerization Polymer Nanocomposites. Polymers 2014, 6, 2037–2050
Polymers 2014, 6(9), 2433-2434; doi:10.3390/polym6092433
Received: 4 August 2014 / Accepted: 7 August 2014 / Published: 22 September 2014
Cited by 1 | PDF Full-text (998 KB) | HTML Full-text | XML Full-text
Abstract The authors wish to make the following corrections to this paper [1]. [...] Full article

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