Showing papers in "Journal of Polymer Science Part B in 2013"
TL;DR: A review of roll-to-roll (R2R) compatible applications for thin-film transistors can be found in this article, where the current status of R2R application within some of the existing research fields such as organic photovoltaics, organic thin film transistors, light-emitting diodes, polymer electrolyte membrane fuel cells and electrochromic devices.
Abstract: With the prospect of extremely fast manufacture of very low cost devices, organic electronics prepared by thin film processing techniques that are compatible with roll-to-roll (R2R) methods are presently receiving an increasing interest. Several technologies using organic thin films are at the point, where transfer from the laboratory to a more production-oriented environment is within reach. In this review, we aim at giving an overview of some of the R2R-compatible techniques that can be used in such a transfer, as well the current status of R2R application within some of the existing research fields such as organic photovoltaics, organic thin film transistors, light-emitting diodes, polymer electrolyte membrane fuel cells, and electrochromic devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
936 citations
TL;DR: Anion exchange membranes (AEMs) provide one possible route to low platinum or platinum-free fuel cells with the potential for facile oxidation of complex fuels beyond hydrogen and methanol as discussed by the authors.
Abstract: This short review is meant to provide the reader with highlights in anion exchange membrane research, describe current needs in the field, and point out promising directions for future work. Anion exchange membranes (AEMs) provide one possible route to low platinum or platinum-free fuel cells with the potential for facile oxidation of complex fuels beyond hydrogen and methanol. AEMs and related stable cationic polymers also have applications in energy storage and other electrochemical technologies such as water electrolyzers and redox flow batteries. While anion exchange membranes have been known for a long time in water treatment applications, materials for electrochemical technology with robust mechanical properties in thin film format have only recently become more widely available. High hydroxide and bicarbonate anion conductivity have been demonstrated in a range of AEM formats, but intrinsic stability of the polymers and demonstration of long device lifetime remain major roadblocks. Novel approaches to stable materials have focused on new types of cations that employ delocalization and steric shielding of the positive center to mitigate nucleophilic attack by hydroxide. A number of promising polymer backbones and membrane architectures have been identified, but limited device testing and a lack of understanding of the degradation mechanisms in operating devices is slowing progress on engineered systems with alkaline fuel cell technology. Our objective is to spur more research in this area to develop fuel cell systems that approach the costs of inexpensive batteries for large-scale applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1727–1735, 2013
380 citations
TL;DR: Anion exchange membranes comprised of a poly(phenylene) backbone and one of five different cationic head-groups are prepared, briefly characterized, and tested for stability in 4 M KOH at 90 °C as mentioned in this paper.
Abstract: Anion exchange membranes comprised of a poly(phenylene) backbone and one of five different cationic head-groups are prepared, briefly characterized, and tested for stability in 4 M KOH at 90 °C. The two membranes with resonance-stabilized cations (benzyl pentamethylguanidinium and benzyl N-methylimidazolium) show large (>25%) decreases in both conductivity and ion exchange capacity (IEC) after just one day of testing. The membrane with benzyl trimethylammonium cations shows a 33% loss of conductivity (14% decrease in IEC) after 14 days while the membrane with trimethylammonium cations attached by a hexamethylene spacer shows the least degradation: a 5% loss of conductivity over 14 days with no accompanying loss in IEC. A similar membrane which has a six-carbon spacer and a ketone adjacent to the phenyl ring shows much lower stability, suggesting that the ketone takes part in degradation reactions. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1736–1742, 2013
250 citations
TL;DR: Graphene has wide potential applications in energy-related systems, mainly because of its unique atom-thick two-dimensional structure, high electrical or thermal conductivity, optical transparency, great mechanical strength, inherent flexibility, and huge specific surface area as discussed by the authors.
Abstract: Graphene has wide potential applications in energy-related systems, mainly because of its unique atom-thick two-dimensional structure, high electrical or thermal conductivity, optical transparency, great mechanical strength, inherent flexibility, and huge specific surface area. For this purpose, graphene materials are frequently blended with polymers to form composites, especially when fabricating flexible devices. Graphene/polymer composites have been explored as electrodes of supercapacitors or lithium ion batteries, counter electrodes of dye-sensitized solar cells, transparent conducting electrodes and active layers of organic solar cells, catalytic electrodes, and polymer electrolyte membranes of fuel cells. In this review, we summarize the recent advances on the synthesis and applications of graphene/polymer composites for energy applications. The challenges and prospects in this field have also been discussed. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
229 citations
TL;DR: A review of recent advances in conjugated polymers and their application in energy storage is presented in this article, with a focus on polyaniline electrodes and their potential for energy storage.
Abstract: This review covers recent advances in conjugated polymers and their application in energy storage. Conjugated polymers are promising cost-effective, lightweight, and flexible electrode materials. The operating principles of conjugated polymers are presented within the framework of their potential for energy storage. Special focus is given to polyaniline electrodes. Recent advances are reviewed including new methods of synthesis, nanostructuring, and assembly. Also, covered are applications that take full advantage of the mechanical properties of conjugated polymers and future applications of these novel materials. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
159 citations
TL;DR: This review highlights recent developments in the field of stimuli-responsive hydrogels, focusing primarily on thin films, with a thickness range between 100 nm to 10 μm, with the potential to advance the fields of medicine and polymer science as useful substrates for “smart” devices.
Abstract: This review highlights recent developments in the field of stimuli-responsive hydrogels, focusing primarily on thin films, with a thickness range between 100 nm to 10 μm. The theory and dynamics of hydrogel swelling is reviewed, followed by specific applications. Gels are classified based on the active stimulus—mechanical, chemical, pH, heat, and light—and fabrication methods, design constraints, and novel stimuli-responses are discussed. Often, these materials display large physiochemical reactions to a relatively small stimulus. Noteworthy materials larger than 10 μm, but with response times on the order of seconds to minutes are also discussed. Hydrogels have the potential to advance the fields of medicine and polymer science as useful substrates for “smart” devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1084–1099
149 citations
TL;DR: In this article, Zhao et al. reported the synthesis of an acrylic elastomer capable of achieving high actuation performance without pre-strain by suppressing electromechanical instability.
Abstract: Prestrain provides high actuation performance in dielectric elastomers (DEs) but increases the bulk, mass, and fatigue of the resulting actuators. Based on our experiments on prestrain-locked interpenetrating polymer films and the model developed by Zhao and Suo, materials with a certain stress–strain relationship should be capable of high strain without prestrain by suppressing electromechanical instability (EMI). Here, we report the synthesis of an acrylic elastomer capable of achieving high actuation performance without prestrain. DE films were directly fabricated by ultraviolet curing of precursors comprising a mixture of acrylate comonomers. Varying the amount of crosslinker comonomer in the precursor allowed us to tune the stress–strain relationship and completely suppress EMI while maintaining high strain performance. Addition of plasticizing agents increased strain sensitivity. The result is a new DE, synthesized from scratch, capable of high actuation strain (>100%), high energy density (>1 J g−1), and good temperature and frequency response without requiring prestretching. The material can be fabricated using conventional coating techniques and the process can allow for high volume throughput of stacked DE actuators. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
120 citations
TL;DR: In this article, single walled carbon nanotubes (SWNT) were stabilized by intrinsi- cally conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) in an aqueous solution.
Abstract: Organic thin film nanocomposites, prepared by liq- uid-phase exfoliation, were investigated for their superior electrical properties and thermoelectric behavior. Single- walled carbon nanotubes (SWNT) were stabilized by intrinsi- cally conductive poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) in an aqueous solution. The electrical conductivity (r) was found to increase linearly as 20 to 95 wt % SWNT. At 95 wt % SWNT, these thin films exhibit metallic electrical conductivity (� 4.0 � 10 5 Sm � 1 ) that is among the
110 citations
TL;DR: Using X-ray diffraction-based pole figures, the microstructure of poly(3-hex-ylthiophene) thin films of varying thicknesses was determined in this article.
Abstract: Using X-ray diffraction-based pole figures, we pres-ent quantitative analysis of the microstructure of poly(3-hex-ylthiophene) thin films of varying thicknesses, which allows usto determine the crystallinity and microstructure at the semi-conductor-dielectric interface. We find that the interface isapproximately one fourth as crystalline as the bulk of the mate-rial. Furthermore, the use of a self-assembled monolayer(SAM) enhances the density of interface-nucleated crystallitesby a factor of 20. Charge transport measurements as a func-tion of film thickness correlate with interface crystallinity.Hence, we establish the crucial role of SAMs as nucleatingagents for increasing carrier mobility in field-effect devices. V C 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys000: 000–000, 2013 KEYWORDS: charge transport; crystallization; structure-propertyrelations; thin films; X-rayINTRODUCTION Organic semiconductors, comprising smallmolecules and conjugated polymers, are a promising materi-als family for next generation electronic devices such as tran-sistors, light-emitting diodes and solar cells. Processes atinterfaces play a very important role in the operation ofthese devices. Because in organic semiconductors the micro-structure is intimately tied to their electronic properties,understanding the effect of surfaces and interfaces on themorphology of these materials is an important component ofoptimizing their performance. In thin film transistors (TFTs)for instance, mobile charge is transported within a few nano-meters of the semiconductor/dielectric interface, which inthe case of bottom-gated devices is the substrate surface.There is significant experimental evidence demonstratingthat controlling the molecular packing and orientation at thedielectric interface can improve the charge carrier mobilityin thin films of poly(3-hexylthiophene) (P3HT), a modelsemicrystalline, semiconducting polymer, by several ordersof magnitude.
91 citations
TL;DR: A series of well-defined poly(3-hexylthiophene)s (P3HTs) of different molecular weight (MW) and high regioregu- larity was investigated for charge transport properties in as-cast and melt-crystallized films as discussed by the authors.
Abstract: A series of well-defined poly(3-hexylthiophene)s (P3HT) of different molecular weight (MW) and high regioregu- larity was investigated for charge transport properties in as- cast and melt-crystallized films. The semicrystalline structure of the P3HT was characterized by X-ray scattering and Atomic force microscopy. Crystallization by cooling from the melt led to a substantial increase in crystallinity and a stronger align- ment of the crystals in comparison to as-cast films. The increase in crystallinity went along with an increase in hole mobility of up to an order of magnitude as measured by the space charge limited current method. Additionally, the hole mobility depended on the long period of P3HT lamellae and consequently on the MW. In compliance with the long period, the charge carrier mobility first increased with the MW before decreasing again at the onset of chain folding. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 00, 000-000
85 citations
TL;DR: In this article, temperature dependent phase behavior of poly(N-isopropylacylamide) (PNIPAM) microgels in water/methanol mixtures of different composition was studied with dynamic light scattering (DLS) and small-angle neutron scattering (SANS).
Abstract: Temperature dependent phase behavior of poly(N-isopropylacylamide) (PNIPAM) microgels in water/methanol mixtures of different composition was studied with dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Using DLS, it is possible to measure the diffusion coefficient, and thus the size of particles exactly and directly; the variation of the phase transition temperature in the different solvents is also easy to detect by this method. With SANS measurements in D2O/MeOD mixtures, some of the DLS results were confirmed. Moreover, SANS measurements give valuable information on the particle structure in different solvents. The experiments were compared with the theory of competitive hydration introduced by Tanaka et al. We found a good agreement of theory and experiment, and obtained the theoretical predictions: around the transition temperature, the composition of the bound methanol along the chains is higher than that of the outer solution, while the whole methanol composition inside the gel is lower. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2013, 51, 1100–1111
TL;DR: In this article, block copolymers of polystyrene-b-poly(vinyl benzyl trimethylammonium tetrafluoroborate) (PS-b-[PVBTMA][BF4]) were synthesized by sequential monomer addition using atom transfer radical polymerization.
Abstract: Block copolymers of polystyrene-b-poly(vinyl benzyl trimethylammonium tetrafluoroborate) (PS-b-[PVBTMA][BF4]) were synthesized by sequential monomer addition using atom transfer radical polymerization. Membranes of the block copolymers were prepared by drop casting from dimethylformamide. Initial evaluation of the microphase separation in these PS-b-[PVBTMA][BF4] materials via SAXS revealed the formation of spherical, cylindrical, and lamellar morphologies. Block copolymers of polystyrene-b-poly(vinyl benzyl trimethylammonium hydroxide) (PS-b-[PVBTMA][OH]) were prepared as polymeric alkaline anion exchange membranes materials by ion exchange from PS-b-[PVBTMA][BF4] with hydroxide in order to investigate the relationship between morphology and ionic conductivity. Studies of humidity [relative humidity (RH)]-dependent conductivity at 80 °C showed that the conductivity increases with increasing humidity. Moreover, the investigation of the temperature-dependent conductivity at RH = 50, 70, and 90% showed a significant effect of grain boundaries in the membranes against the formation of continuous conductive channels, which is an important requirement for achieving high ion conductivity. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1751–1760, 2013
TL;DR: In this paper, the authors investigated the breakdown properties of poly(ethylene terephthalate) (PET) and poly(vinylidene fluoride-co-tetrafluoroethylene) [P(VDF-TFE)] copolymer.
Abstract: Polymer films with enhanced dielectric and breakdown properties are essential for the production of high energy density polymer film capacitors. By capitalizing on the synergistic effects of forced assembly nanolayer coextrusion and biaxial orientation, polymer multilayer films using poly(ethylene terephthalate) (PET) and a poly(vinylidene fluoride-co-tetrafluoroethylene) [P(VDF-TFE)] copolymer were produced. These films exhibited breakdown fields, under a divergent field using needle/plane electrodes, as high as 1000 kV mm−1. The energy densities of these same materials, under a uniform electric field measured using plane/plane electrodes, were as high as 16 J cm−3. The confined morphologies of both PET and P(VDF-TFE) were correlated to the observed breakdown properties and damage zones. On-edge P(VDF-TFE) crystals induced from solid-state biaxial stretching enhanced the effective P(VDF-TFE) layer dielectric constant and therefore increased the dielectric contrast between the PET and P(VDF-TFE) layers. This resulted in additional charge buildup at the layer interface producing larger tree diameters and branches and ultimately increasing the breakdown and energy storage properties. In addition to energy storage and breakdown properties, the hysteresis behavior of these materials was also evaluated. By varying the morphology of the P(VDF-TFE) layer, the low-field dielectric loss (or ion migration behavior) could be manipulated, which in turn also changed the observed hysteresis behavior. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 882–896
TL;DR: SiO2/polyvinylidene fluoride (PVDF) composite nanofiber-coated polypropylene (PP) nonwoven membranes were prepared by electrospinning of SiO 2/PV DF dispersions onto both sides of PP non-wovens as mentioned in this paper.
Abstract: SiO2/polyvinylidene fluoride (PVDF) composite nanofiber-coated polypropylene (PP) nonwoven membranes were prepared by electrospinning of SiO2/PVDF dispersions onto both sides of PP nonwovens. The goal of this study was to combine the good mechanical strength of PP nonwoven with the excellent electrochemical properties of SiO2/PVDF composite nanofibers to obtain a new high-performance separator. It was found that the addition of SiO2 nanoparticles played an important role in improving the overall performance of these nanofiber-coated nonwoven membranes. Among the membranes with various SiO2 contents, 15% SiO2/PVDF composite nanofiber-coated PP nonwoven membranes provided the highest ionic conductivity of 2.6 × 10−3 S cm−1 after being immersed in a liquid electrolyte, 1 mol L−1 lithium hexafluorophosphate in ethylene carbonate, dimethyl carbonate and diethyl carbonate. Compared with pure PVDF nanofiber-coated PP nonwoven membranes, SiO2/PVDF composite fiber-coated PP nonwoven membranes had greater liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO2/PVDF composite fiber-coated PP nonwoven membrane separators were assembled into lithium/lithium iron phosphate cells and demonstrated high cell capacities and good cycling performance at room temperature. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1719–1726
TL;DR: In this article, the authors present a theory and simulation study of polymer grafted nanoparticles with chemical and physical heterogeneity in grafts to calculate the effective interactions and morphology as a function of chemistry, molecular weights, grafting densities, and so forth.
Abstract: Macroscopic properties of polymer nanocomposites depend on the microscopic composite morphology of the constituent nanoparticles and polymer matrix. One way to control the spatial arrangement of the nanoparticles in the polymer matrix is by grafting the nanoparticle surfaces with polymers that can tune the effective interparticle interactions in the polymer matrix. A fundamental understanding of how graft and matrix polymer chemistries and molecular weight, grafting density, and nanoparticle size, and chemistry affect interparticle interactions is needed to design the appropriate polymer ligands to achieve the target morphology. Theory and simulations have proven to be useful tools in this regard due to their ability to link molecular level interactions to the morphology. In this feature article, we present our recent theory and simulation studies of polymer grafted nanoparticles with chemical and physical heterogeneity in grafts to calculate the effective interactions and morphology as a function of chemistry, molecular weights, grafting densities, and so forth. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: In this paper, a combination of solution casting and solvent-nonsolvent exchange (phase inversion) has been applied to generate asymmetric membranes with highly ordered hexagonally packed cylinders with perpendicular orientation composed of polystyrene-block-poly(ethylene oxide).
Abstract: For the first time the combination of solution casting and solvent–nonsolvent exchange (phase inversion) has been applied to generate asymmetric membranes with highly ordered hexagonally packed cylinders with perpendicular orientation composed of polystyrene-block-poly(ethylene oxide). The influence of parameters like solvent composition and evaporation time on the membrane formation is presented. The development is based on a study of the solution behavior by dynamic light scattering and the precipitation behavior of the cylinder forming diblock copolymer by turbidity measurements from different solvent and nonsolvent systems. The water flux properties, as an important membrane characteristic, show a time dependent behavior, due to swelling of the polyethylene oxide blocks. The morphologies of the membranes are imaged by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: In this article, a remarkable electrochemical activation of polypyrrole chains by doping with redox-active diphenylamine sulfonate anions was demonstrated, which can not only serve as anionic counterions to enhance electrochemical activity of the polymer chains, but also contribute their redox capacity to the material.
Abstract: We demonstrate here a remarkable electrochemical activation of polypyrrole chains by doping with redox-active diphenylamine sulfonate anions. The organic redox dopant can not only serve as anionic counterions to enhance electrochemical activity of the polymer chains, but also contributes their redox capacity to the material. This organic-polymer composite exhibits a quite high reversible capacity of 115 mA h g−1, excellent rate capability and cycling stability, capable of serving as a low cost, and renewable cathode for Na-ion batteries. Since the chemical doping method is simple and easily extendable for a large variety of organic anions and polymer networks, it is possible to adopt this new strategy for creating low cost and electrochemically active polymer materials for widespread electric storage applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: In this paper, the effect of thermal stress on the morphology of polymer:fullerene bulk heterojunction (BHJ) solar cells is investigated in the darkness, and it is shown that light exposure slows down fullerene crystallization and phase separation induced at elevated temperatures.
Abstract: For an increased lifetime of polymer:fullerene bulk heterojunction (BHJ) solar cells, an understanding of the chemical and morphological degradation phenomena taking place under operational conditions is crucial. Phase separation between polymer and fullerene induced by thermal stress has been pointed out as a major issue to overcome. While often the effect of thermal stress on the morphology of polymer:fullerene BHJ is investigated in the darkness, here we observe that light exposure slows down fullerene crystallization and phase separation induced at elevated temperatures. The observed photo-stabilizing effect on active layer morphology is quite independent on the polymer and is attributed to light-induced dimerization of the fullerene. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1209–1214
TL;DR: In this article, a flexible electrochromic active matrix addressed display, including 8 × 8 pixels, is demonstrated by using solution processing based on standard printing and coating manufacturing techniques, and the display is shown to work well in indoor environments.
Abstract: A flexible electrochromic active matrix addressed display, including 8 × 8 pixels, is demonstrated by using solution processing based on standard printing and coating manufacturing techniques. Each ...
TL;DR: In this paper, three-component multilayer films with ATBTATBTA configuration were fabricated using forced assembly multi-layer coextrusion for novel dielectric systems.
Abstract: Unique three-component multilayer films with ATBTATBTA configuration were fabricated using forced assembly multilayer coextrusion for novel dielectric systems. The dielectric breakdown strength, displacement–electric field hysteresis, and dielectric spectroscopy of 65-layer polycarbonate (PC)/tie/ poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) were investigated with various tie materials. Three different tie materials, poly(methyl methacrylate) (PMMA), styrene-co-acrylonitrile copolymer with 30% acrylonitrile content (SAN30), and poly(ethylene terephthalate-co-1,4-cycohexanedimethylene terephthalate) (PETG) were chosen owing to their various degrees of interaction with either P(VDF-HFP) or PC. The 65-layer PC/ PMMA/P(VDF-HFP) films exhibited a 25% enhancement in breakdown properties, 50% higher energy density, 40% smaller hysteresis loop areas, and orders of magnitude slower ion migration relative to the 33-layer PC/P(VDF-HFP) control. These property improvements are mainly attributed to the localized interactions at PMMA/P(VDF-HFP) and PMMA/PC interfaces, forming interphase regions. The modified PMMA/P(VDF-HFP) interphase region can effectively hinder the migration of impurity ions in P(VDF-HFP), reducing their mobility within the layer. Additionally, a small fraction of PMMA can lead to slightly increased dielectric constant of the composite films owing to strong interaction between PMMA and P(VDF-HFP). The other two systems with PETG and SAN30 as tie layers exhibited marginal improvements in dielectric properties owing to their weaker interactions with the P(VDF-HFP) layers. VC 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51,
TL;DR: An effective technique of using click coupled graphene to obtain high-performance polymer nanocomposites is presented in this paper, where poly(e-caprolactone) (PCL)-click coupled graphene sheet (GS) reinforcing fillers are synthesized by the covalent functionalization of graphene oxide with PCL, and subsequently the PCL-GS as a reinforcing filler was incorporated into a shape memory polyurethane matrix by solution casting.
Abstract: An effective technique of using click coupled graphene to obtain high-performance polymer nanocomposites is presented. Poly(e-caprolactone) (PCL)-click coupled graphene sheet (GS) reinforcing fillers are synthesized by the covalent functionalization of graphene oxide with PCL, and subsequently the PCL-GS as a reinforcing filler was incorporated into a shape memory polyurethane matrix by solution casting. The PCL-click coupled GS has shown excellent interaction with the polyurethane matrix, and as a consequence, the mechanical properties, thermal stability, thermal conductivity, and thermo-responsive shape memory properties of the resulting nanocomposite films could be enhanced remarkably. In particular, for polyurethane nanocomposites incorporated with 2% PCL-GS, the breaking stress, Young's modulus, elongation-at-break, and thermal stability have been improved by 109%, 158%, 28%, and 71 °C, respectively. This click coupling protocol offers the possibility to fully combine the extraordinary performance of GSs with the properties of polyurethane. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: The recent contributions of quasielastic neutron scattering techniques (time of flight, backscattering, and neutron spin echo) to the characterization and understanding of dynamical processes in soft materials based on polymers are analyzed in this article.
Abstract: The recent (from 2010 onward) contributions of quasielastic neutron scattering techniques (time of flight, backscattering, and neutron spin echo) to the characterization and understanding of dynamical processes in soft materials based on polymers are analyzed. The selectivity provided by the combination of neutron scattering and isotopic—in particular, proton/deuterium—labeling allows the isolated study of chosen molecular groups and/or components in a system. This opportunity, together with the capability of neutrons to provide space/time resolution at the relevant length scales in soft matter, allows unraveling the nature of the large variety of molecular motions taking place in materials of increasing complexity. As a result, recent relevant works can be found dealing with dynamical process which associated characteristic lengths and nature are as diverse as, for example, phenyl motions in a glassy linear homopolymer like polystyrene and the chain dynamics of a polymer adsorbed on dispersed clay platelets. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: In this paper, the authors describe cloning structural characterization and optical properties of a reflectin-based domain, refCBA, from reflectin 1a of Hawaiian bobtail squid, Euprymna scolopes.
Abstract: : Reflectins are a unique group of structural proteins involved in dynamic optical systems in cephalopods that modulate incident light or bioluminescence. We describe cloning structural characterization, and optical properties of a reflectinbased domain, refCBA, from reflectin 1a of Hawaiian bobtail squid, Euprymna scolopes. Thin films created from the recombinant protein refCBA display interesting optical features when the recombinant protein is appropriately organized. RefCBA was cloned and expressed as a soluble protein enabling purification, with little structural organization found using Fourier transform infrared spectroscopy and circular dichroism. Single-layer and multi-layer thin films of refCBA were then produced by flow coating and spin coating, and displayed colors due to thin film interference. Diffraction experiments showed the assemblies were ordered enough to work as diffraction gratings to generate diffraction patterns. Nano-spheres and lamellar microstructures of refCBA samples were observed by scanning electron microscopy and atomic force microscopy. Despite the reduced complexity of the refCBA protein compared to natural reflectins, unique biomaterials with similar properties to reflectins were generated by self-assembled reflectin-based refCBA molecules.
TL;DR: In this article, the possibility to use Ionic Polymer Metal Composites as a class of materials relevant to the realization of post silicon smart systems is discussed and three main aspects of this new technology, fabrication methods, modeling, and applications are described with emphasis to most recent results.
Abstract: Smart systems adapt to the surrounding environments in a number of ways. They are capable to scavenge energy from available sources, sense and elaborate external stimuli and adequately react. Electro Active Polymers are playing a main role in the realization of smart systems for applications if fields such as bio inspired and autonomous robotics, medicine, and aerospace. This paper focus on the possibility to use Ionic Polymer Metal Composites as a class of materials relevant to the realization of post silicon smart systems. The three main aspects of this new technology, i.e., fabrication methods, modeling, and applications are described with emphasis to most recent results. Attention is given to main challenges and shortcomings to be solved for technology, modelling, and control of IPMC based devices that need to be solved before this new technology can be fully exploited in real world applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013
TL;DR: In this paper, a review of different approaches taken to generate tailored polymer brush systems through surface-initiated polymerizations as well as patterning techniques is presented, and the possibility of separating polymer brushes to create free-standing membranes is discussed in terms of methods and characterization.
Abstract: While polymer brush systems continue to grow in popularity, so does their complexity and sophistication. Advances in polymerization and specific functionalization methods have led to novel applications in diverse research fields. The marriage of top-down lithography with bottom-up brush processing is becoming increasingly important in the development and progress of nanotechnology. The aim of this review is to examine different approaches taken to generate tailored polymer brush systems through surface-initiated polymerizations as well as patterning techniques. Detaching polymer brushes to create free-standing membranes is also highlighted and discussed in terms of methods and characterization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1457–1472
TL;DR: There is an ongoing effort to elucidate the molecular level behaviors of polymers in water by using sum frequency generation vibrational spectroscopy (SFG), which stands out for its utility in probing buried interfaces in situ and in real time without disrupting interfacial chemistry as discussed by the authors.
Abstract: Industrial plastics, biomedical polymers and numerous other polymeric systems are contacted with water for everyday functions and after disposal. Probing the interfacial molecular interactions between widely used polymers and water yields valuable information that can be extrapolated to macroscopic polymer/water interfacial behaviors so scientists can better understand polymer bio-compatibility, hygroscopic tendencies and improve upon beneficial polymer behavior in water. There is an ongoing concerted effort to elucidate the molecular level behaviors of polymers in water by using sum frequency generation vibrational spectroscopy (SFG). SFG stands out for its utility in probing buried interfaces in situ and in real time without disrupting interfacial chemistry. Included in this review are SFG water interfacial studies performed on poly(methacrylate) and (acrylate)s, poly(dimethyl siloxane)s, poly(ethylene glycol)s, poly(electrolyte)s and other polymer types. The driving forces behind common water/polymer interfacial molecular features will be discussed as well as unique molecular reorientation phenomena and resulting macroscopic behaviors from microscopic polymer rearrangement. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: In this article, a review of recent work with hydrogels based on poly(hydroxyethyl acrylate), mostly copolymers with a second hydrophobic polymer and silica nanocomposites is presented.
Abstract: Polymer hydrogels have attracted much interest in recent years based on numerous applications mainly in biotechnology and medicine. For the knowledge-based design and development of new materials for these and similar applications, it is essential to understand better the hydration properties of hydrogels and of polymers in general. With this term, we mean the particular organization of water in the hydrogel, which determines the properties of the water component, typically different than those of bulk water, and the impact of water on the properties of the polymer matrix itself. In this review, we focus on recent work with hydrogels based on poly(hydroxyethyl acrylate), mostly copolymers with a second hydrophobic polymer and silica nanocomposites. The combination of water sorption/diffusion, thermal and dielectric studies, by fully exploiting the capabilities of each individual technique, proves essential in providing significant information on particular aspects of hydration, such as water uptake, water organization, and diffusion coefficients; glass transition and plasticization; water and polymer dynamics; protonic conductivity, and in revealing interesting correlations between these particular aspects. In the outlook similarities and differences to other related systems, such as protein-water and polymer solutions in non-polar solvents, are stressed in the perspective of a broader study. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: Several solvent-free processing methods to disperse multiwalled carbon nanotubes (MWCNTs) in bisphenol F-based epoxy resin were investigated, including the use of a microfluidizer (MF), planetary shear mixer (PSM), ultrasonication (US), and combinations as mentioned in this paper.
Abstract: Several solvent-free processing methods to disperse multiwalled carbon nanotubes (MWCNTs) in bisphenol F-based epoxy resin were investigated, including the use of a microfluidizer (MF), planetary shear mixer (PSM), ultrasonication (US) and combinations. The processed mixture was cured with diethyl toluene diamine. Three complimentary techniques were used to characterize the dispersion of the MWCNTs in cured composite samples: optical microscopy, micro Raman spectroscopy, and scanning electron microscopy (SEM). For sample MF + PSM, optical micrographs and Raman images showed reduced agglomeration and a homogeneous distribution of MWCNTs in the epoxy matrix. SEM analysis of fractured specimen after tensile testing revealed breakage of nanotubes along the fracture surface of the composite. A comparison of the MWCNT dispersion in the epoxy samples processed using different methods showed that a combination of MF and PSM processing yields a more homogeneous sample than the PSM or US + PSM processed samples. Mechanical testing of the composites showed about 15% improvement in the tensile strength of samples processed by the MF + PSM method over other methods. Thermogravimetric analysis (TGA) results showed a small decrease in the onset degradation temperature for poorly dispersed samples produced by PSM compared with the well-mixed samples (MF + PSM). These results strongly suggest that the MF + PSM processing method yield better-dispersed and stronger MWCNT/epoxy composites. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013
TL;DR: In this paper, the most recent results in this area focusing on the last 2-3 years, and also some background information are discussed, and potential perspectives of this area are outlined.
Abstract: Core-shell microgels are of increasing interest as smart carriers of catalysts, as sensors, or as building blocks for colloidal superstructures. In the context of colloidal assemblies, photonic applications are probably the most promising ones. This progress report presents and discusses the most recent results in this area focusing on the last 2-3 years, and also gives some background information. In addition, potential perspectives of this area will be outlined. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1073-1083