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Polymers, Volume 7, Issue 4 (April 2015) , Pages 592-776

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Open AccessArticle
Effect of Artificial Weathering on PLA/Nanocomposite Molecular Weight Distribution
Polymers 2015, 7(4), 760-776; https://doi.org/10.3390/polym7040760
Received: 23 January 2015 / Revised: 3 April 2015 / Accepted: 16 April 2015 / Published: 22 April 2015
Cited by 12 | Viewed by 2434 | PDF Full-text (8904 KB) | HTML Full-text | XML Full-text
Abstract
The reduction of polylactide acid (PLA) molecular weight for amorphous and semicrystalline grade nanocomposites with 5 wt% load of organomodified montmorillonite Cloisite30B (C30B) was investigated in periods of up to 360 h under artificial weathering. A correlation between artificial and natural weathering was [...] Read more.
The reduction of polylactide acid (PLA) molecular weight for amorphous and semicrystalline grade nanocomposites with 5 wt% load of organomodified montmorillonite Cloisite30B (C30B) was investigated in periods of up to 360 h under artificial weathering. A correlation between artificial and natural weathering was established. The nanocomposites were prepared by mixing the C30B in PLA matrix using two stages of extrusion followed by injection molding. In addition, we also studied materials without C30B in PLA matrix prepared by a single stage of injection, as well as with two stages of extrusion followed by injection, in order to assess thermal effects. XRD (X-ray diffraction) and TEM (Transmission electron microscope) were used to determine the layer dispersion of the C30B within the PLA. An increase in the interlayer spacing of a sandwich structure corresponding to a partial exfoliation of the C30B was found, leading to the creation of small particles at nanoscale of one (1.29 nm) to eight (11.76 nm) platelets. Also, GPC (Gel permeation chromatography) was used to evaluate the molecular weight decay of neat PLA and its nanocomposites due to thermal processing and subsequent artificial weathering exposure. From thermal processing, a more significant decrease of polydispersity in amorphous PLA than in semicrystalline PLA counterparts could be observed. First order fitting of molecular weight decay of samples versus time of exposure under artificial weathering was found for all materials tested. It was observed that the addition of clay favored PLA degradation in amorphous PLA, in comparison with semicrystalline PLA in both thermal processing and artificial weathering. Moreover, a possible effect of C30B interactions with PLA chains under artificial weathering could be postulated. Full article
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Open AccessArticle
Characterization of Novel Castor Oil-Based Polyurethane Polymer Electrolytes
Polymers 2015, 7(4), 747-759; https://doi.org/10.3390/polym7040747
Received: 15 January 2015 / Revised: 23 March 2015 / Accepted: 10 April 2015 / Published: 16 April 2015
Cited by 21 | Viewed by 2776 | PDF Full-text (958 KB) | HTML Full-text | XML Full-text
Abstract
Castor oil-based polyurethane as a renewable resource polymer has been synthesized for application as a host in polymer electrolyte for electrochemical devices. The polyurethane was added with LiI and NaI in different wt% to form a film of polymer electrolytes. The films were [...] Read more.
Castor oil-based polyurethane as a renewable resource polymer has been synthesized for application as a host in polymer electrolyte for electrochemical devices. The polyurethane was added with LiI and NaI in different wt% to form a film of polymer electrolytes. The films were characterized by using attenuated total reflectance-Fourier transform infrared spectroscopy, dynamic mechanical analysis, electrochemical impedance spectroscopy, linear sweep voltammetry and transference number measurement. The highest conductivity of 1.42 × 10−6 S cm−1 was achieved with the addition of 30 wt% LiI and 4.28 × 10−7 S·cm−1 upon addition of 30 wt% NaI at room temperature. The temperature dependence conductivity plot indicated that both systems obeyed Arrhenius law. The activation energy for the PU-LiI and PU-NaI systems were 0.13 and 0.22 eV. Glass transition temperature of the synthesized polyurethane decreased from −15.8 °C to ~ −26 to −28 °C upon salts addition. These characterizations exhibited the castor oil-based polyurethane polymer electrolytes have potential to be used as alternative membrane for electrochemical devices. Full article
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Open AccessReview
Polymers and Dyes: Developments and Applications
Polymers 2015, 7(4), 717-746; https://doi.org/10.3390/polym7040717
Received: 5 March 2015 / Revised: 8 April 2015 / Accepted: 9 April 2015 / Published: 15 April 2015
Cited by 37 | Viewed by 3868 | PDF Full-text (1334 KB) | HTML Full-text | XML Full-text
Abstract
Amongst functional macromolecules, the combination of polymers and dyes is a research field of great potential with regard to high-performance materials. Accordingly, colored polymers have become increasingly important as materials for miscellaneous technical applications in recent years while also being a major part [...] Read more.
Amongst functional macromolecules, the combination of polymers and dyes is a research field of great potential with regard to high-performance materials. Accordingly, colored polymers have become increasingly important as materials for miscellaneous technical applications in recent years while also being a major part of everyday life. For instance, dye-containing polymers are nowadays widely applied in medicine, painting industries, analytics and gas separation processes. Since these applications are obviously connected to the dye’s nature, which is incorporated into the corresponding polymers, the affinity of certain polymers to dyes is exploited in wastewater work-ups after (textile) dyeing procedures. In this review, we wish to point out the great importance of dye-containing polymers, with a comprehensive scope and a focus on azo, triphenylmethane, indigoid, perylene and anthraquinone dyes. Since a large number of synthetic approaches towards the preparation of such materials can be found in the literature, an elaborated overview of different preparation techniques is given as well. Full article
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Open AccessArticle
Tailoring Confinement: Nano-Carrier Synthesis via Z-RAFT Star Polymerization
Polymers 2015, 7(4), 695-716; https://doi.org/10.3390/polym7040695
Received: 19 February 2015 / Revised: 18 March 2015 / Accepted: 2 April 2015 / Published: 10 April 2015
Cited by 2 | Viewed by 2517 | PDF Full-text (2127 KB) | HTML Full-text | XML Full-text
Abstract
A new pathway to nano-sized hollow-sphere particles from six-arm star polymers with an amphiphilic core-corona structure, synthesized in a four-step-procedure by means of reversible addition-fragmentation chain transfer (RAFT) polymerization is presented, in order to achieve more stable and versatile nano-container systems, which could [...] Read more.
A new pathway to nano-sized hollow-sphere particles from six-arm star polymers with an amphiphilic core-corona structure, synthesized in a four-step-procedure by means of reversible addition-fragmentation chain transfer (RAFT) polymerization is presented, in order to achieve more stable and versatile nano-container systems, which could be applied in the fields of drug delivery or catalyst storage. Star-shaped amphiphilic, diblock copolymers serve as globular platforms for synthesizing uniform hollow structures. By the introduction of monomer units carrying UV-cross-linkable dimethyl maleimido functionalities into the outer sphere of these star polymers, the carrier’s shell could be stabilized under UV-irradiation. After removal of the RAFT-core—constituting the central hub of the star polymer—by aminolysis, the carrier is ready for loading. Full article
(This article belongs to the Special Issue Complex Macromolecular Architectures)
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Open AccessArticle
Enhancement in the Glass Transition Temperature in Latent Thiol-Epoxy Click Cured Thermosets
Polymers 2015, 7(4), 680-694; https://doi.org/10.3390/polym7040680
Received: 19 March 2015 / Revised: 27 March 2015 / Accepted: 31 March 2015 / Published: 9 April 2015
Cited by 23 | Viewed by 3428 | PDF Full-text (849 KB) | HTML Full-text | XML Full-text
Abstract
Tri and tetrafunctional thiol were used as curing agent for diglycidyl ether of bisphenol A (DGEBA) catalyzed by a commercially available amine precursor, LC-80. Triglycidyl isocianurate (TGIC) was added in different proportions to the mixture to increase rigidity and glass transition temperature ( [...] Read more.
Tri and tetrafunctional thiol were used as curing agent for diglycidyl ether of bisphenol A (DGEBA) catalyzed by a commercially available amine precursor, LC-80. Triglycidyl isocianurate (TGIC) was added in different proportions to the mixture to increase rigidity and glass transition temperature (Tg). The cooperative effect of increasing functionality of thiol and the presence of TGIC in the formulation leads to an increased Tg without affecting thermal stability. The kinetics of the curing of mixtures was studied by calorimetry under isothermal and non-isothermal conditions. The latent characteristics of the formulations containing amine precursors were investigated by rheometry and calorimetry. The increase in the functionality of the thiol produces a slight decrease in the storage lifetime of the mixture. The materials obtained with tetrathiol as curing agent showed the highest values of Young’s modulus and Tg. Full article
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Open AccessArticle
Exploring the Full Potential of Reversible Deactivation Radical Polymerization Using Pareto-Optimal Fronts
Polymers 2015, 7(4), 655-679; https://doi.org/10.3390/polym7040655
Received: 27 February 2015 / Revised: 26 March 2015 / Accepted: 1 April 2015 / Published: 9 April 2015
Cited by 13 | Viewed by 3535 | PDF Full-text (3880 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The use of Pareto-optimal fronts to evaluate the full potential of reversible deactivation radical polymerization (RDRP) using multi-objective optimization (MOO) is illustrated for the first time. Pareto-optimal fronts are identified for activator regenerated electron transfer atom transfer radical polymerization (ARGET ATRP) of butyl [...] Read more.
The use of Pareto-optimal fronts to evaluate the full potential of reversible deactivation radical polymerization (RDRP) using multi-objective optimization (MOO) is illustrated for the first time. Pareto-optimal fronts are identified for activator regenerated electron transfer atom transfer radical polymerization (ARGET ATRP) of butyl methacrylate and nitroxide mediated polymerization (NMP) of styrene. All kinetic and diffusion parameters are literature based and a variety of optimization paths, such as temperature and fed-batch addition programs, are considered. It is shown that improvements in the control over the RDRP characteristics are possible beyond the capabilities of batch or isothermal RDRP conditions. Via these MOO-predicted non-classical polymerization procedures, a significant increase of the degree of microstructural control can be obtained with a limited penalty on the polymerization time; specifically, if a simultaneous variation of various polymerization conditions is considered. The improvements are explained based on the relative importance of the key reaction rates as a function of conversion. Full article
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Open AccessArticle
Interval Analysis: A New Tool for the Characterization of an Epoxy-Amine/Aluminum System
Polymers 2015, 7(4), 644-654; https://doi.org/10.3390/polym7040644
Received: 10 February 2015 / Revised: 23 March 2015 / Accepted: 30 March 2015 / Published: 3 April 2015
Cited by 1 | Viewed by 1886 | PDF Full-text (3326 KB) | HTML Full-text | XML Full-text
Abstract
Epoxy-amine/aluminum chemical systems or sandwich structures with and without interphase formation are prepared using two different curing cycles and are characterized with dielectric spectroscopy. The sample without interphase formation is obtained when the reaction between epoxy and amine groups is favored, which occurs [...] Read more.
Epoxy-amine/aluminum chemical systems or sandwich structures with and without interphase formation are prepared using two different curing cycles and are characterized with dielectric spectroscopy. The sample without interphase formation is obtained when the reaction between epoxy and amine groups is favored, which occurs at high temperature. The interphase formation results from the reaction between the amine group and aluminum surface at room temperature. Dielectric spectra are fitted using the Set Inversion Via Interval Analysis (SIVIA) algorithm applied to DiElectric spectroscopy algorithm (SADE) developed using the method of intervals analysis. A new approach is implemented using a sum of Debye relaxations to optimize and guarantee the fitting. The results achieved show a distribution of relaxation times, which always take place at the same time as demonstrated. In this study, five Debye relaxations were found which fit the β-relaxation with our model. Finally, we showed that the more intensive of our five β -relaxations follows the Arrhenius law. Full article
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Open AccessArticle
Polymethylmethacrylate/Polyacrylonitrile Membranes via Centrifugal Spinning as Separator in Li-Ion Batteries
Polymers 2015, 7(4), 629-643; https://doi.org/10.3390/polym7040629
Received: 5 February 2015 / Revised: 16 March 2015 / Accepted: 27 March 2015 / Published: 1 April 2015
Cited by 32 | Viewed by 3410 | PDF Full-text (1947 KB) | HTML Full-text | XML Full-text
Abstract
Electrospun nanofiber membranes have been extensively studied as separators in Li-ion batteries due to their large porosity, unique pore structure, and high electrolyte uptake. However, the electrospinning process has some serious drawbacks, such as low spinning rate and high production cost. The centrifugal [...] Read more.
Electrospun nanofiber membranes have been extensively studied as separators in Li-ion batteries due to their large porosity, unique pore structure, and high electrolyte uptake. However, the electrospinning process has some serious drawbacks, such as low spinning rate and high production cost. The centrifugal spinning technique can be used as a fast, cost-effective and safe technique to fabricate high-performance fiber-based separators. In this work, polymethylmethacrylate (PMMA)/polyacrylonitrile (PAN) membranes with different blend ratios were produced via centrifugal spinning and characterized by using different electrochemical techniques for use as separators in Li-ion batteries. Compared with commercial microporous polyolefin membrane, centrifugally-spun PMMA/PAN membranes had larger ionic conductivity, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. Centrifugally-spun PMMA/PAN membrane separators were assembled into Li/LiFePO4 cells and these cells delivered high capacities and exhibited good cycling performance at room temperature. In addition, cells using centrifugally-spun PMMA/PAN membrane separators showed superior C-rate performance compared to those using microporous polypropylene (PP) membranes. It is, therefore, demonstrated that centrifugally-spun PMMA/PAN membranes are promising separator candidate for high-performance Li-ion batteries. Full article
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Open AccessArticle
Multi-Scale Simulation of Hyperbranched Polymers
Polymers 2015, 7(4), 610-628; https://doi.org/10.3390/polym7040610
Received: 28 January 2015 / Revised: 21 March 2015 / Accepted: 23 March 2015 / Published: 30 March 2015
Cited by 5 | Viewed by 1920 | PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
In a previous work, we described a multi-scale protocol for the simulation of the conformation and dynamics of macromolecules that was applied to dendrimer molecules proving its predictive capability by comparison with experimental data. That scheme is now employed in order to predict [...] Read more.
In a previous work, we described a multi-scale protocol for the simulation of the conformation and dynamics of macromolecules that was applied to dendrimer molecules proving its predictive capability by comparison with experimental data. That scheme is now employed in order to predict conformational properties (radius of gyration) and overall hydrodynamic properties (translational diffusion and intrinsic viscosity) of hyperbranched molecules in dilute solution. For that purpose, we use a very simple coarse-grained bead-and-spring model whose parameters are not adjusted against experimental properties but they are obtained from previous atomic-level (Langevin) simulations of small fragments of real hyperbranched polymers. In addition, we devise a method to generate structures with different degree of branching. The Monte Carlo simulation technique was used to generate the set conformations of the coarse-grained model. In spite of the difficulties of reproducing experimental data of highly polydisperse entities (in terms of both molecular weight and topology) without using adjustable parameters, the results of this paper show that the proposed methodology allows for qualitative predictions of the behavior of such complex systems and lead us to conclude that, after some improvement, acceptable quantitative predictions can be achieved. Full article
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Open AccessArticle
Block Co-Polymers for Nanolithography: Rapid Microwave Annealing for Pattern Formation on Substrates
Polymers 2015, 7(4), 592-609; https://doi.org/10.3390/polym7040592
Received: 9 December 2014 / Revised: 6 March 2015 / Accepted: 23 March 2015 / Published: 30 March 2015
Cited by 1 | Viewed by 2913 | PDF Full-text (13674 KB) | HTML Full-text | XML Full-text
Abstract
The integration of block copolymer (BCP) self-assembled nanopattern formation as an alternative lithographic tool for nanoelectronic device fabrication faces a number of challenges such as defect densities, feature size, pattern transfer, etc. Key barriers are the nanopattern process times and pattern formation on [...] Read more.
The integration of block copolymer (BCP) self-assembled nanopattern formation as an alternative lithographic tool for nanoelectronic device fabrication faces a number of challenges such as defect densities, feature size, pattern transfer, etc. Key barriers are the nanopattern process times and pattern formation on current substrate stack layers such as hard masks (e.g., silicon nitride, Si3N4). We report a rapid microwave assisted solvothermal (in toluene environments) self-assembly and directed self-assembly of a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP thin films on planar and topographically patterned Si3N4 substrates. Hexagonally arranged, cylindrical structures were obtained and good pattern ordering was achieved. Factors affecting BCP self-assembly, notably anneal time and temperature, were studied and seen to have significant effects. Graphoepitaxy within the topographical structures provided long range, translational alignment of the patterns. The effect of surface topography feature size and spacing was investigated. The solvothermal microwave based technique used to provide periodic order in the BCP patterns showed significant promise and ordering was achieved in much shorter periods than more conventional thermal and solvent annealing methods. The implications of the work in terms of manufacturing technologies are discussed. Full article
(This article belongs to the Special Issue Advances in Polymer Brushes)
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