Showing papers in "Polymers in 2013"
TL;DR: Graphene nanoplatelets (xGnP) were investigated as a nano-reinforcement filler in poly(lactic acid)(PLA)/poly(ethylene glycol)(PEG) blends by the melt blending method as discussed by the authors.
Abstract: Graphene nanoplatelets (xGnP) were investigated as a novel nano-reinforcement filler in poly(lactic acid)(PLA)/poly(ethylene glycol)(PEG) blends by the melt blending method. PLA was first plasticized by PEG in order to improve its flexibility and thereby overcome its problem of brittleness. Then, xGnP was incorporated into the PLA/PEG blend. The prepared nanocomposites exhibited a significant improvement in tensile properties at a low xGnP loading. The tensile properties demonstrated the addition of 0.3 wt% of xGnP led to an increase of up to 32.7%, 69.5% and 21.9% in tensile strength, tensile modulus and elongation at break of the nanocomposites respectively, compared to PLA/PEG blend. X-ray diffraction (XRD) patterns showed the presence of a peak around 26.5○ in PLA/PEG/xGnP nanocomposites which corresponds to the characteristic peak of xGnP. The nanocomposites also shows enhanced thermal stability compared with PLA/PEG blend in thermogravimetry analysis (TGA). The enhancement to some extent of the tensile properties of the PLA/PEG/xGnP nanocomposites can be ascribed to the homogeneous dispersion and orientation of the xGnP nanoplatelets in the polymer matrix and strong interfacial interaction between both components. The scanning electron microscopy (SEM) image of PLA/PEG/0.3 wt% xGnP displays good uniformity and more homogenous morphology. Good uniformity of composites indicates a good degree of dispersion of the xGnp and therefore results in good tensile and thermal properties.
400 citations
TL;DR: The field of ring opening polymerization (ROP) has been a rapidly growing and industrially important area of research as discussed by the authors, and the literature up to 2012 has been considered but the citations refer to detailed reviews and key papers describing not only the latest developments but also the evolution of the current state of the art.
Abstract: This short, introductory review covers the still rapidly growing and industrially important field of ring opening polymerization (ROP). The review is organized according to mechanism (radical ROP (RROP), cationic ROP (CROP), anionic ROP (AROP) and ring-opening metathesis polymerization (ROMP)) rather than monomer classes. Nevertheless, the different groups of cyclic monomers are considered (olefins, ethers, thioethers, amines, lactones, thiolactones, lactams, disulfides, anhydrides, carbonates, silicones, phosphazenes and phosphonites) and the mechanisms by which they can be polymerized involving a ring-opening polymerization. Literature up to 2012 has been considered but the citations selected refer to detailed reviews and key papers, describing not only the latest developments but also the evolution of the current state of the art.
315 citations
TL;DR: In this article, the authors provide an outline of the membrane requirements for FO/PRO and the new methods and materials in membrane preparation, as well as an overview of the new membrane requirements and materials used for membrane preparation.
Abstract: In the past four decades, membrane development has occurred based on the demand in pressure driven processes. However, in the last decade, the interest in osmotically driven processes, such as forward osmosis (FO) and pressure retarded osmosis (PRO), has increased. The preparation of customized membranes is essential for the development of these technologies. Recently, several very promising membrane preparation methods for FO/PRO applications have emerged. Preparation of thin film composite (TFC) membranes with a customized polysulfone (PSf) support, electorspun support, TFC membranes on hydrophilic support and hollow fiber membranes have been reported for FO/PRO applications. These novel methods allow the use of other materials than the traditional asymmetric cellulose acetate (CA) membranes and TFC polyamide/polysulfone membranes. This review provides an outline of the membrane requirements for FO/PRO and the new methods and materials in membrane preparation.
202 citations
TL;DR: In this article, the authors discuss and compare eleven different multiscale computational techniques falling under three categories: (i) coarse-graining methods for generic polymers; (ii) systematic coarse-grounding methods and (iii) multiple-scale-bridging methods.
Abstract: The mechanical and physical properties of polymeric materials originate from the interplay of phenomena at different spatial and temporal scales. As such, it is necessary to adopt multiscale techniques when modeling polymeric materials in order to account for all important mechanisms. Over the past two decades, a number of different multiscale computational techniques have been developed that can be divided into three categories: (i) coarse-graining methods for generic polymers; (ii) systematic coarse-graining methods and (iii) multiple-scale-bridging methods. In this work, we discuss and compare eleven different multiscale computational techniques falling under these categories and assess them critically according to their ability to provide a rigorous link between polymer chemistry and rheological material properties. For each technique, the fundamental ideas and equations are introduced, and the most important results or predictions are shown and discussed. On the one hand, this review provides a comprehensive tutorial on multiscale computational techniques, which will be of interest to readers newly entering this field; on the other, it presents a critical discussion of the future opportunities and key challenges in the multiscale modeling of polymeric materials and how these methods can help us to optimize and design new polymeric materials.
183 citations
TL;DR: A review of the state-of-the-art of poly(2-oxazoline) preparation can be found in this article, where the authors compare the desktop-planned synthetic strategy and the variability of their properties for dedicated applications.
Abstract: The polymer class of poly(2-oxazoline)s currently is under intensive investigation due to the versatile properties that can be tailor-made by the variation and manipulation of the functional groups they bear. In particular their utilization in the biomedic(in)al field is the subject of numerous studies. Given the mechanism of the cationic ring-opening polymerization, a plethora of synthetic strategies exists for the preparation of poly(2-oxazoline)s with dedicated functionality patterns, comprising among others the functionalization by telechelic end-groups, the incorporation of substituted monomers into (co)poly(2-oxazoline)s, and polymeranalogous reactions. This review summarizes the current state-of-the-art of poly(2-oxazoline) preparation and showcases prominent examples of poly(2-oxazoline)-based materials, which are retraced to the desktop-planned synthetic strategy and the variability of their properties for dedicated applications.
130 citations
TL;DR: In this paper, a review of hierarchical primary and secondary structures of nanofibers is presented, including helical, buckled, and beads-on-a-string fibers.
Abstract: Traditional electrospun nanofibers have a myriad of applications ranging from scaffolds for tissue engineering to components of biosensors and energy harvesting devices. The generally smooth one-dimensional structure of the fibers has stood as a limitation to several interesting novel applications. Control of fiber diameter, porosity and collector geometry will be briefly discussed, as will more traditional methods for controlling fiber morphology and fiber mat architecture. The remainder of the review will focus on new techniques to prepare hierarchically structured fibers. Fibers with hierarchical primary structures—including helical, buckled, and beads-on-a-string fibers, as well as fibers with secondary structures, such as nanopores, nanopillars, nanorods, and internally structured fibers and their applications—will be discussed. These new materials with helical/buckled morphology are expected to possess unique optical and mechanical properties with possible applications for negative refractive index materials, highly stretchable/high-tensile-strength materials, and components in microelectromechanical devices. Core-shell type fibers enable a much wider variety of materials to be electrospun and are expected to be widely applied in the sensing, drug delivery/controlled release fields, and in the encapsulation of live cells for biological applications. Materials with a hierarchical secondary structure are expected to provide new superhydrophobic and self-cleaning materials.
120 citations
TL;DR: This review aims to divulge the basic principles of designing polyphosphazenes for drug and gene delivery and portray the huge potential of these extremely versatile materials for such applications.
Abstract: Poly[(organo)phosphazenes] are a unique class of extremely versatile polymers with a range of applications including tissue engineering and drug delivery, as hydrogels, shape memory polymers and as stimuli responsive materials. This review aims to divulge the basic principles of designing polyphosphazenes for drug and gene delivery and portray the huge potential of these extremely versatile materials for such applications. Polyphosphazenes offer a number of distinct advantages as carriers for bioconjugates; alongside their completely degradable backbone, to non-toxic degradation products, they possess an inherently and uniquely high functionality and, thanks to recent advances in their polymer chemistry, can be prepared with controlled molecular weights and narrow polydispersities, as well as self-assembled supra-molecular structures. Importantly, the rate of degradation/hydrolysis of the polymers can be carefully tuned to suit the desired application. In this review we detail the recent developments in the chemistry of polyphosphazenes, relevant to drug and gene delivery and describe recent investigations into their application in this field.
112 citations
TL;DR: In this paper, the authors summarized the recent research progress in the underlying mechanisms behind the shape memory effect (SME) and some newly discovered shape memory phenomena in polymeric materials.
Abstract: This review paper summarizes the recent research progress in the underlying mechanisms behind the shape memory effect (SME) and some newly discovered shape memory phenomena in polymeric materials. It is revealed that most polymeric materials, if not all, intrinsically have the thermo/chemo-responsive SME. It is demonstrated that a good understanding of the fundamentals behind various types of shape memory phenomena in polymeric materials is not only useful in design/synthesis of new polymeric shape memory materials (SMMs) with tailored performance, but also helpful in optimization of the existing ones, and thus remarkably widens the application field of polymeric SMMs.
102 citations
TL;DR: In this article, the use of cotton fiber (CF) as a filler in poly(butylene succinate) (PBS) and the effect of silane treatment on the mechanical properties, thermal stability, and biodegradability of PBS/CF composites are investigated.
Abstract: In this study, the use of cotton fiber (CF) as a filler in poly(butylene succinate) (PBS) and the effect of silane treatment on the mechanical properties, thermal stability, and biodegradability of PBS/CF composites are investigated The results showed that the tensile strength of PBS was improved (15%–78%) with the incorporation of CF (10–40 wt%) and was further increased (25%–118%) when CF was treated with a silane coupling agent Scanning electron microscopy (SEM) observation of the fracture surfaces of PBS/CF composites showed that there was slight improvement in fiber-matrix compatibility Thermogravimetric (TG) analysis showed that the thermal stability of the composites was lower than that of neat PBS and decreased with increasing filler loading The biobased carbon content of the composites increased with increasing CF content The incorporation of CF (with and without silane treatment) in PBS significantly increased the biodegradation rate of the composites
98 citations
TL;DR: This review provides a current status report of the field concerning preparation of fibrous mats based on biodegradable and conducting polymers and can be combined to get free-standing nanomembranes and nanofibers that retain the better properties of their corresponding individual components.
Abstract: This review provides a current status report of the field concerning preparation of fibrous mats based on biodegradable (e.g., aliphatic polyesters such as polylactide or polycaprolactone) and conducting polymers (e.g., polyaniline, polypirrole or polythiophenes). These materials have potential biomedical applications (e.g., tissue engineering or drug delivery systems) and can be combined to get free-standing nanomembranes and nanofibers that retain the better properties of their corresponding individual components. Systems based on biodegradable and conducting polymers constitute nowadays one of the most promising solutions to develop advanced materials enable to cover aspects like local stimulation of desired tissue, time controlled drug release and stimulation of either the proliferation or differentiation of various cell types. The first sections of the review are focused on a general overview of conducting and biodegradable polymers most usually employed and the explanation of the most suitable techniques for preparing nanofibers and nanomembranes (i.e., electrospinning and spin coating). Following sections are organized according to the base conducting polymer (e.g., Sections 4–6 describe hybrid systems having aniline, pyrrole and thiophene units, respectively). Each one of these sections includes specific subsections dealing with applications in a nanofiber or nanomembrane form. Finally, miscellaneous systems and concluding remarks are given in the two last sections.
86 citations
TL;DR: In this article, pure polyamide 6 (PA6) and carbon nanotube (CNT) composite samples with 0.5 weight percent loading of pristine or functionalized CNTs were made using a solution mixing technique.
Abstract: Pure polyamide 6 (PA6) and polyamide 6/carbon nanotube (PA6/CNT) composite samples with 0.5 weight percent loading of pristine or functionalized CNTs were made using a solution mixing technique. Modification of nanotube surface as a result of chemical functionalization was confirmed through the presence of lattice defects as examined under high-resolution transmission electron microscope and absorption bands characteristic of carboxylic, sulfonic and amine chemical groups. Microstructural examination of the cryogenically fractured surfaces revealed qualitative information regarding CNT dispersion within PA6 matrix and interfacial strength. X-ray diffraction studies indicated formation of thermodynamically more stable α-phase crystals. Thermogravimetric analysis revealed that CNT incorporation delayed onset of thermal degradation by as much as 70 °C in case of amine-functionalized CNTs, thus increasing thermal stability of the composites. Furthermore, addition of amine-functionalized CNTs caused an increase in crystallization and melting temperatures from the respective values of 177 and 213 °C (for neat PA6) to 211 and 230 °C (for composite), respectively.
TL;DR: In this article, the authors present a survey of the literature on the assisted fabrication of carbon nanotubes and graphene-based nanocomposites with a variety of polymers, including fluoropolymers, hydrocarbon polymers and polyacrylates, cellulose and polymeric ionic liquids.
Abstract: Carbon nanotubes (CNTs) and graphene sheets are the most promising fillers for polymer nanocomposites due to their superior mechanical, electrical, thermal optical and gas barrier properties, as well as high flame-retardant efficiency. The critical challenge, however, is how to uniformly disperse them into the polymer matrix to achieve a strong interface for good load transfer between the two. This problem is not new but more acute in CNTs and graphene, both because they are intrinsically insoluble and tend to aggregate into bundles and because their surfaces are atomically smooth. Over the past decade, imidazolium ionic liquids (Imi-ILs) have played a multifunctional role (e.g., as solvents, dispersants, stabilizers, compatibilizers, modifiers and additives) in the fabrication of polymer composites containing CNTs or graphene. In this review, we first summarize the liquid-phase exfoliation, stabilization, dispersion of CNTs and graphene in Imi-ILs, as well as the chemical and/or thermal reduction of graphene oxide to graphene with the aid of Imi-ILs. We then present a full survey of the literature on the Imi-ILs assisted fabrication of CNTs and graphene-based nanocomposites with a variety of polymers, including fluoropolymers, hydrocarbon polymers, polyacrylates, cellulose and polymeric ionic liquids. Finally, we give a future outlook in hopes of facilitating progress in this emerging area.
TL;DR: In this article, the morphological and structural features of conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT) and organic photovoltaic cell (OPV), etc.] in terms of crystallinity, packing of polymer chains and connection between crystal domains.
Abstract: The morphological and structural features of the conjugated polymer films play an important role in the charge transport and the final performance of organic optoelectronics devices [such as organic thin-film transistor (OTFT) and organic photovoltaic cell (OPV), etc.] in terms of crystallinity, packing of polymer chains and connection between crystal domains. This review will discuss how the conjugated polymer solidify into, for instance, thin-film structures, and how to control the molecular arrangement of such functional polymer architectures by controlling the polymer chain rigidity, polymer solution aggregation, suitable processing procedures, etc. These basic elements in intrinsic properties and processing strategy described here would be helpful to understand the correlation between morphology and charge transport properties and guide the preparation of efficient functional conjugated polymer films correspondingly.
TL;DR: In this paper, a separation procedure combining molecularly imprinted-solid phase extraction (MI-SPE) was developed for the isolation of melamine, which showed a better affinity toward melamine compared to non imprinted polymer (NIP) with a maximum binding capacity of 53.01 mg/g MIP.
Abstract: In this paper, a separation procedure combining molecularly imprinted-solid phase extraction (MI-SPE) was developed for the isolation of melamine. The molecularly imprinted polymer (MIP) was prepared using precipitation polymerization method where melamine as template, 9-vinylcarbazole as functional monomer, ethtylene glycol dimethacrylate as a cross-linker and benzoyl peroxide as initiator. An off-line MI-SPE method followed by ultra-performance liquid chromatography detection of melamine was established. MIP showed a better affinity toward melamine compared to non imprinted polymer (NIP) with a maximum binding capacity of 53.01 mg/g MIP. Based on the correlation coefficients, the kinetic study indicated that the adsorption of melamine by MIP fit a pseudo-second order model. From isotherm study, adsorption of melamine by MIP increased when the concentration of melamine increased and followed a Freundlich isotherm model, which indicates the sorption can be described by multilayer sorption. The interference study proved that MIP has better binding capacity towards melamine if compared to NIP due to specific sites of melamine occurred in MIP particles.
TL;DR: In this paper, a mechanism of the glycolysis of poly(ethylene terephthalate) PET catalyzed by [Bmim]ZnCl3 was proposed.
Abstract: Poly(ethlyene terephthalate) waste from a local market was depolymerized by ethylene glycol (EG) in the presence of Lewis acidic ionic liquids [Bmim]ZnCl3 and the qualitative analysis showed that bis(hydroxyethyl) terephthalate was the main product. Compared with ionic liquid [Bmim]Cl, the Lewis acidic ionic liquids showed highly catalytic activity in the glycolysis of poly(ethylene terephthalate) PET. Significantly, the conversion of PET and the yield of bis(hydroxyethyl) terephthalate were achieved at 100% and 83.8% with low catalyst ([Bmim]ZnCl3) loading (0.16 wt %). Investigation also showed that the catalytic activity of [Bmim]ZnCl3 was higher than that of [Bmim]MnCl3. Catalyst [Bmim]ZnCl3 can be reused up to five times and 1H-NMR results show that the recovered catalyst is similar to the fresh one. A mechanism of the glycolysis of PET catalyzed by [Bmim]ZnCl3 was proposed.
TL;DR: A review of the state of the art in the synthesis of well-defined glycopolymers by Reversible-Deactivation Radical Polymerization (RDRP) from its inception in 1998 until August 2012 can be found in this paper.
Abstract: This review summarizes the state of the art in the synthesis of well-defined glycopolymers by Reversible-Deactivation Radical Polymerization (RDRP) from its inception in 1998 until August 2012. Glycopolymers architectures have been successfully synthesized with four major RDRP techniques: Nitroxide-mediated radical polymerization (NMP), cyanoxyl-mediated radical polymerization (CMRP), atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization. Over 140 publications were analyzed and their results summarized according to the technique used and the type of monomer(s) and carbohydrates involved. Particular emphasis was placed on the experimental conditions used, the structure obtained (comonomer distribution, topology), the degree of control achieved and the (potential) applications sought. A list of representative examples for each polymerization process can be found in tables placed at the beginning of each section covering a particular RDRP technique.
TL;DR: In this article, the state of the art regarding advances and challenges in synthesis and applications of specialty polymers and composites derived from cellulose, hemicellulose and lignin, with a brief assessment of genetic modification as a route to tailor crop plants for specific applications.
Abstract: Since the realization that global sustainability depends on renewable sources of materials and energy, there has been an ever-increasing need to develop bio-based polymers that are able to replace petroleum-based polymers. Research in this field has shown strong potential in generating high-performance functionalized polymers from plant biomass. With the anticipated large-scale production of lignocellulosic biomass, lignin, cellulose and hemicellulosic polysaccharides will be abundantly available renewable feedstocks for biopolymers and biocomposites with physico-chemical properties that match or exceed those of petroleum-based compounds. This review examines the state of the art regarding advances and challenges in synthesis and applications of specialty polymers and composites derived from cellulose, hemicellulose and lignin, ending with a brief assessment of genetic modification as a route to tailor crop plants for specific applications.
TL;DR: Self-assembly and content-release behavior of nanoscale polybutadiene- b-poly(ethylene oxide) (PB-PEO) hybrid phospholipid/block copolymer vesicles can be tuned by the mixing ratio of the amphiphiles.
Abstract: Hybrid phospholipid/block copolymer vesicles, in which the polymeric membrane is blended with phospholipids, display interesting self-assembly behavior, incorporating the robustness and chemical versatility of polymersomes with the softness and biocompatibility of liposomes. Such structures can be conveniently characterized by preparing giant unilamellar vesicles (GUVs) via electroformation. Here, we are interested in exploring the self-assembly and properties of the analogous nanoscale hybrid vesicles (ca. 100 nm in diameter) of the same composition prepared by film-hydration and extrusion. We show that the self-assembly and content-release behavior of nanoscale polybutadiene- b-poly(ethylene oxide) (PB-PEO)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) hybrid phospholipid/block copolymer vesicles can be tuned by the mixing ratio of the amphiphiles. In brief, these hybrids may provide alternative tools for drug delivery purposes and molecular imaging/sensing applications and clearly open up new avenues for further investigation.
TL;DR: In this paper, a hydrophobic poly(ionic liquid) of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonyl)imide) (PVI-TFSI) was synthesized for the separation of methyl blue and chromium ions [Cr(VI)] from water.
Abstract: The hydrophobic poly(ionic liquid) of poly(3-ethyl-1-vinylimidazolium bis(trifluoromethanesulfonyl)imide) (PVI-TFSI) containing imidazolium cations and bis(trifluoromethanesulfonyl)imide anions was synthesized for the separation of methyl blue and chromium ions [Cr(VI)] from water. The adsorption of methyl blue and Cr(VI) in PVI-TSFI/water system reached equilibrium stage within 60 min and 12 h, and the maximum adsorbed percentage for methyl blue and Cr(VI) was 97.6% and 98.0%, respectively. The adsorption regi me of either methyl blue or Cr(VI) for PVI-TFSI was in correspondence with the Langmuir adsorption model. The maximum adsorption capacity of PVI-TFSI for methyl blue and Cr(VI) was determined as 476.2 and 17.9 mg/g, respectively. The hydrophobic poly(ionic liquid) with a remarkable adsorbent capacity of methyl blue and Cr(VI) can be conveniently synthesized and shows potential in water treatment for the effective separation of organic dyes or heavy metal ions.
TL;DR: In this paper, a review of continuum modeling and coarse-grained molecular dynamics methods, which connect atomistic simulations and single-molecule experiments with the observed microscopic or mesoscale properties of soft-matter systems essential to our understanding of cells, particularly those involved in sculpting and remodeling cell membranes.
Abstract: The physiological properties of biological soft matter are the product of collective interactions, which span many time and length scales. Recent computational modeling efforts have helped illuminate experiments that characterize the ways in which proteins modulate membrane physics. Linking these models across time and length scales in a multiscale model explains how atomistic information propagates to larger scales. This paper reviews continuum modeling and coarse-grained molecular dynamics methods, which connect atomistic simulations and single-molecule experiments with the observed microscopic or mesoscale properties of soft-matter systems essential to our understanding of cells, particularly those involved in sculpting and remodeling cell membranes.
TL;DR: A series of polypeptoid homopolymers bearing short (C1-C5) side chains of degrees of polymerization of 10-100 were studied with respect to thermal stability, glass transition and melting points as discussed by the authors.
Abstract: A series of polypeptoid homopolymers bearing short (C1–C5) side chains of degrees of polymerization of 10–100 are studied with respect to thermal stability, glass transition and melting points. Thermogravimetric analysis of polypeptoids suggests stability to >200 °C. The study of the glass transition temperatures by differential scanning calorimetry revealed two dependencies. On the one hand an extension of the side chain by constant degree of polymerization decrease the glass transition temperatures (Tg) and on the other hand a raise of the degree of polymerization by constant side chain length leads to an increase of the Tg to a constant value. Melting points were observed for polypeptoids with a side chain comprising not less than three methyl carbon atoms. X-ray diffraction of polysarcosine and poly(N-ethylglycine) corroborates the observed lack of melting points and thus, their amorphous nature. Diffractograms of the other investigated polypeptoids imply that crystalline domains exist in the polymer powder.
TL;DR: In this paper, the potential of esterified tannins as plastic additives in poly(lactic acid) (PLA) was evaluated, and the results suggest scope for the use of tannin esters possessing longer ester chain length as plastic additive.
Abstract: Reported is a study evaluating the potential of esterified tannins as plastic additives in poly(lactic acid) (PLA). Tannin esterification using anhydrides was investigated as a route to synthesize tannin esters possessing varying ester chain length and degree of substitution (DS). Esterification decreased the tannin UV absorbance, predominately in the UVB region. However, tannin materials with longer ester chain lengths exhibited melt behaviors suitable for processing in plastics. On compounding into PLA, tannin hexanoate esters lowered the PLA glass transition by 5–6 °C. Shorter chain length tannin esters had a reduced effect on PLA polymer properties. The PLA flexural properties were significantly altered with stiffness decreases of up to 15% depending on ester chain length and loading. Artificial weathering of modified the PLA samples suggests the presence of tannin esters may confer a protection role to PLA on extended exposure. Overall, results suggest scope for the use of tannin esters possessing longer ester chain length as plastic additives.
TL;DR: In this article, two linking methodologies were designed in conjunction with a living anionic polymerization system for the synthesis of novel multiblock polymers, composed of three or more blocks, difficult to be synthesized by sequential polymerization.
Abstract: This article reviews the successful development of two specially designed linking methodologies in conjunction with a living anionic polymerization system for the synthesis of novel multiblock polymers, composed of three or more blocks, difficult to be synthesized by sequential polymerization. The first methodology with the use of a new heterofunctional linking agent, 2-(4-chloromethylphenyl)ethyldimethylchlorosilane (1), was developed for the synthesis of multiblock polymers containing poly(dimethylsiloxane) (PDMS) blocks. This methodology is based on the selective reaction of the chain-end silanolate anion of living PDMS, with the silyl chloride function of 1, and subsequent linking reaction of the resulting ω-chain-end-benzyl chloride-functionalized polymer with either a living anionic polymer or living anionic block copolymer. With this methodology, various multiblock polymers containing PDMS blocks, up to the pentablock quintopolymer, were successfully synthesized. The second methodology using an α-phenylacrylate (PA) reaction site was developed for the synthesis of multiblock polymers composed of all-vinyl polymer blocks. In this methodology, an α-chain-end-PA-functionalized polymer or block copolymer, via the living anionic polymerization, was first prepared and, then, reacted with appropriate living anionic polymer or block copolymer to link the two polymer chains. As a result, ACB (BCA), BAC (CAB), (AB)n, (AC)n, ABA, ACA, BCB, and ABCA multiblock polymers, where A, B, and C were polystyrene, poly(2-vinylpyridine), and poly(methyl methacrylate) segments, could be successfully synthesized. The synthesis of triblock copolymers, BAB, CAC, and CBC, having molecular asymmetry in both side blocks, was also achieved. Furthermore, the use of living anionic polymers, derived from many other monomers, categorized as either of styrene, 2-vinylpyridine, or methyl methacrylate in monomer reactivity, in the linking methodology enabled the number of synthetically possible block polymers to be greatly increased. Once again, all of the block polymers synthesized by these methodologies are new and cannot be synthesized at all by sequential polymerization. They were well-defined in block architecture and precisely controlled in block segment.
TL;DR: In this article, EGCG was loaded to hydrogel prepared from ionic interaction between an optimized concentration of gelatin and γ-polyglutamic acid (γ-PGA), with ethylcarbodiimide (EDC) as the crosslinker.
Abstract: The antioxidant property and other health benefits of the most abundant catechin, epigallocatechin gallate (EGCG), are limited because of poor stability and permeability across intestine. Protecting the EGCG from the harsh gastrointestinal tract (GIT) environment can help to increase its bioavailability following oral administration. In this study, EGCG was loaded to hydrogel prepared from ionic interaction between an optimized concentration of gelatin and γ-polyglutamic acid (γ-PGA), with ethylcarbodiimide (EDC) as the crosslinker. Physicochemical characterization of hydrogel was done using Fourier transform-infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The dependence of the swelling degree (SD) of the hydrogel to the amount of gelatin, γ-PGA, EDC, swelling time and pH was determined. A high SD of the crosslinked hydrogel was noted at pH 4.5, 6.8
TL;DR: In this article, the design rules, synthesis schemes, and characteristics of this unique polymeric material are reviewed and an in-depth discussion ranging from the polymer material design to the cell performance in consideration of commercialization requirements.
Abstract: Elevated-temperature (100~200 °C) polymer electrolyte membrane (PEM) fuel cells have many features, such as their high efficiency and simple system design, that make them ideal for residential micro-combined heat and power systems and as a power source for fuel cell electric vehicles. A proton-conducting solid-electrolyte membrane having high conductivity and durability at elevated temperatures is essential, and phosphoric-acid-containing polymeric material synthesized from cross-linked polybenzoxazine has demonstrated feasible characteristics. This paper reviews the design rules, synthesis schemes, and characteristics of this unique polymeric material. Additionally, a membrane electrode assembly (MEA) utilizing this polymer membrane is evaluated in terms of its power density and lifecycle by an in situ accelerated lifetime test. This paper also covers an in-depth discussion ranging from the polymer material design to the cell performance in consideration of commercialization requirements.
TL;DR: In this paper, the sol gel method was employed to prepare peroxopolytungstic acid (P-PTA), Palladium chloride and Polyvinyl pyrrolidone (PVP) was dissolved in the sol Pd:WO3 = 10% molar ratio.
Abstract: Pd doped WO3 fibers were synthesized by electro-spinning. The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA). Palladium chloride and Polyvinyl pyrrolidone (PVP) was dissolved in the sol Pd:WO3 = 10% molar ratio. The prepared sol was loaded into a syringe connected to a high voltage of 18.3 kV and electrospun fibers were collected on the alumina substrates. Scanning electron microscope (SEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques were used to analyze the crystal structure and chemical composition of the fibers after heat treatment at 500 °C. Resistance-sensing measurements exhibited a sensitivity of about 30 at 500 ppm hydrogen in air, and the response and recovery times were about 20 and 30 s, respectively, at 300 °C. Hydrogen gas sensing mechanism of the sensor was also studied.
TL;DR: The protein-polymer interacting behavior and overall morphology is envisioned to aid in clarifying protein-protein interactions and are thought to entail some interesting new functions and properties which will ultimately lead to novel bio-hybrid materials.
Abstract: Protein aggregation and protein self-assembly is an important occurrence in natural systems, and is in some form or other dictated by biopolymers. Very obvious influences of biopolymers on protein assemblies are, e.g., virus particles. Viruses are a multi-protein assembly of which the morphology is dictated by poly-nucleotides namely RNA or DNA. This “biopolymer” directs the proteins and imposes limitations on the structure like the length or diameter of the particle. Not only do these bionanoparticles use polymer-directed self-assembly, also processes like amyloid formation are in a way a result of directed protein assembly by partial unfolded/misfolded biopolymers namely, polypeptides. The combination of proteins and synthetic polymers, inspired by the natural processes, are therefore regarded as a highly promising area of research. Directed protein assembly is versatile with respect to the possible interactions which brings together the protein and polymer, e.g., electrostatic, v.d. Waals forces or covalent conjugation, and possible combinations are numerous due to the large amounts of different polymers and proteins available. The protein-polymer interacting behavior and overall morphology is envisioned to aid in clarifying protein-protein interactions and are thought to entail some interesting new functions and properties which will ultimately lead to novel bio-hybrid materials.
TL;DR: This review provides a current status report of the field concerning peptide-synthetic polymer hybrids and the attractive properties, displayed in solution or in the solid state, together with the potential applications of this type of macromolecules or supramolecular systems are highlighted.
Abstract: Hybrid block copolymers based on peptides and synthetic polymers, displaying different types of topologies, offer new possibilities to integrate the properties and functions of biomacromolecules and synthetic polymers in a single hybrid material. This review provides a current status report of the field concerning peptide-synthetic polymer hybrids. The first section is focused on the different synthetic approaches that have been used within the last three years for the preparation of peptide-polymer hybrids having different topologies. In the last two sections, the attractive properties, displayed in solution or in the solid state, together with the potential applications of this type of macromolecules or supramolecular systems are highlighted.
TL;DR: In this article, the influence of plasticizer content on elongational flow properties of cellulose acetate (CA) was investigated and the area under the Rheotens curve was analyzed.
Abstract: Elongational flow properties of polymer melts are very important for numerous polymer processing technologies such as blown film extrusion or foam extrusion. Rheotens tests were conducted to investigate the influence of plasticizer content on elongational flow properties of cellulose acetate (CA). Triethyl citrate (TEC) was used as plasticizer. Melt strength decreases whereas melt extensibility increases with increasing plasticizer content. Melt strength was further studied as a function of zero shear viscosity. The typical draw resonance of the Rheotens curve shifts to higher drawdown velocity and the amplitude of the draw resonance decreases with increasing TEC content. With respect to foam extrusion, not only are melt strength and melt extensibility important but the elongational behavior at low strain rates and the area under the Rheotens curve are also significant. Therefore, elongational viscosity as well as specific energy input were calculated and investigated with respect to plasticizer content. Preliminary foam extrusion tests of externally plasticized CA using chemical blowing agents confirm the results from rheological characterization.
TL;DR: The release of potassium ion and calcium ion via the control of cross-linking density of a poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogel containing 1 mol % 2-methacryloyloysloxyethyl phosphorylcholine (MPC) and 5 mol % oligo(ethylene glycol) monomethacrylated [OEG(400)MA] was investigated.
Abstract: In an attempt to recreate the microenvironment necessary for directed hematopoietic stem cell differentiation, control over the amount of ions available to the cells is necessary. The release of potassium ion and calcium ion via the control of cross-linking density of a poly(2-hydroxyethyl methacrylate) (pHEMA)-based hydrogel containing 1 mol % 2-methacryloyloxyethyl phosphorylcholine (MPC) and 5 mol % oligo(ethylene glycol) (400) monomethacrylate [OEG(400)MA] was investigated. Tetra(ethylene glycol) diacrylate (TEGDA), the cross-linker, was varied over the range of 1–12 mol %. Hydrogel discs (ϕ = 4.5 mm and h = 2.0 mm) were formed by UV polymerization within silicone isolators to contain 1.0 M CaCl2 and 0.1 M KCl, respectively. Isothermal release profiles, were measured at 37 °C in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid sodium salt (HEPES) buffer using either calcium ion or potassium ion selective electrodes (ISE). The resulting release profiles were found to be independent of cross-linking density. Average (n = 3) release profiles were fit to five different release models with the Korsmeyer-Peppas equation, a porous media transport model, exhibiting the greatest correlation (R2 > 0.95). The diffusion exponent, n was calculated to be 0.24 ± 0.02 and 0.36 ± 0.04 for calcium ion and potassium ion respectively indicating non-Fickian diffusion. The resulting diffusion coefficients were calculated to be 2.6 × 10−6 and 11.2 × 10−6 cm2/s, which compare well to literature values of 2.25 × 10−6 and 19.2 × 10−6 cm2/s for calcium ion and potassium ion, respectively.