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Crosslinked Poly (crosslinked + poly)
Selected AbstractsSynthesis and characterization of polyelectrolyte hydrogels with controlled swelling behaviourPOLYMER INTERNATIONAL, Issue 12 2001Ayman M Atta Abstract Copolymerization of sulfopropyl methacrylate potassium salt (K-SPMA) and 2-acrylamido-2-methyl propane sulfonic acid (AMPS) has been studied in the range 10,90% K-SPMA in the feedstock. The reactivity ratios have been determined for K-SPMA/AMPS copolymers. The copolymer compositions, utilized for determining the reactivity ratio, have been determined from nitrogen content. Crosslinked poly(AMPS) and K-SPMA/AMPS copolymers were prepared in water in the presence of potassium persulfate as initiator and N,N -methylene bisacrylamide (MBA) as tetrafunctional crosslinker. Irradiation of K-SPMA and AMPS with an electron-beam was carried out at 50,wt% aqueous solution with low pH and irradiation dose 40,120,kGy. The swelling behaviour of highly crosslinked K-SPMA/AMPS copolymer polyelectrolyte gels in aqueous medium was studied in the presence of different types of salts. The crosslink density, the average molecular weight between the crosslinks and the dissociation constant (pKa) of the crosslinked polymer were determined from stress,strain measurements. © 2001 Society of Chemical Industry [source] Fabrication and properties of crosslinked poly(propylene carbonate maleate) gel polymer electrolyte for lithium-ion batteryJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Xiaoyuan Yu Abstract The poly(propylene carbonate maleate) (PPCMA) was synthesized by the terpolymerization of carbon dioxide, propylene oxide, and maleic anhydride. The PPCMA polymer can be readily crosslinked using dicumyl peroxide (DCP) as crosslinking agent and then actived by absorbing liquid electrolyte to fabricate a novel PPCMA gel polymer electrolyte for lithium-ion battery. The thermal performance, electrolyte uptake, swelling ratio, ionic conductivity, and lithium ion transference number of the crosslinked PPCMA were then investigated. The results show that the Tg and the thermal stability increase, but the absorbing and swelling rates decrease with increasing DCP amount. The ionic conductivity of the PPCMA gel polymer electrolyte firstly increases and then decreases with increasing DCP ratio. The ionic conductivity of the PPCMA gel polymer electrolyte with 1.2 wt % of DCP reaches the maximum value of 8.43 × 10,3 S cm,1 at room temperature and 1.42 × 10,2 S cm,1 at 50°C. The lithium ion transference number of PPCMA gel polymer electrolyte is 0.42. The charge/discharge tests of the Li/PPCMA GPE/LiNi1/3Co1/3Mn1/3O2 cell were evaluated at a current rate of 0.1C and in voltage range of 2.8,4.2 V at room temperature. The results show that the initial discharge capacity of Li/PPCMA GPE/LiNi1/3Co1/3Mn1/3 O2 cell is 115.3 mAh g,1. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Structure and drug release in a crosslinked poly(ethylene oxide) hydrogelJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2007Boris Y. Shekunov Abstract Hydrogels are a continuously expanding class of pharmaceutical polymers designed for sustained or controlled drug release. The structure and intermolecular interactions in such systems define their macroscopic properties. The aim of this study was to investigate the mechanism of swelling, drug impregnation, and drug release from poly(ethylene oxide) (PEO) gel crosslinked by urethane bonds. A combination of SAXS/WAXS/SANS techniques enabled us to determine the phase transition between lamellar and extended gel network, and to apply different descriptions of crystallinity, based on lamellar and crystal lattice structures. It is shown that even low (1,7% w/w) loading of model drugs acetaminophen and caffeine, produced significant disorder in the polymer matrix. This effect was particularly pronounced for acetaminophen due to its specific ability to form complexes with PEO. The drug-release profiles were analyzed using a general cubic equation, proposed for this work, which allowed us to determine the gel hydration velocity. The results indicate that the release profiles correlate inversely with the polymer crystallinity. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1320,1330, 2007 [source] Low-frequency dielectric spectroscopy as a tool for studying the compatibility between pharmaceutical gels and mucous tissueJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2003Helene HäGerström Abstract This interdisciplinary work demonstrates how low-frequency dielectric spectroscopy, a technique that is frequently used within physics, can be used to assess the possibilities of intimate surface contact between a polymer gel and mucous tissue, which is generally considered to be the first step in the mucoadhesion process. The dielectric responses of five different gels, of freshly excised porcine nasal mucosa and of systems made by combining the two were measured. All spectra were modeled by a Randles electric circuit containing a diffusion element, a barrier resistance in parallel with a capacitance, and a high-frequency resistance. The results were used to create a measure of the compatibility between the gel and the mucus, which we have named the compatibility factor. Thus, the compatibility factor provides us with a measure of the ease with which a charged species passes the interface between a gel and the mucus layer. The compatibility factor is calculated from the high frequency (kHz region) response of the gel, of the mucosa, and of the combined system. The two highest compatibility factors in this study were obtained for gels based on crosslinked poly(acrylic acid) and chitosan, which was in agreement with the results from mucoadhesion measurements that were performed using a tensile strength method. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1869,1881, 2003 [source] Analysis of the swelling dynamics of crosslinked P(N -iPAAm- co -MAA) copolymers, the corresponding homopolymers and their interpenetrating networks.POLYMER INTERNATIONAL, Issue 6 2003Kinetics of water penetration into the gel above the pKaof MAA comonomeric units Abstract The effect of composition on the swelling kinetics of a series of crosslinked poly(N -isopropylacrylamide)s [P(N -iPAAm)] and poly(methacrylic acid)s [P(MAA)], their statistical copolymers P(N -iPAAm- co -MAA), and some sequential interpenetrating networks (IPNs) has been studied at pHs above the pKa of MAA comonomeric units. The swelling process of the hydrogels upon immersion in buffer solutions was monitored by the weight change as a function of time. First-order kinetics apply better than second-order kinetics which fail, especially for predicting swelling equilibrium values. However, hydrogels presenting hydrogen bonding between MAA and N -iPAAm units do not obey either first-order or second-order kinetics. The high n values found indicate that the swelling process is mostly controlled by polymer relaxation. Copyright © 2003 Society of Chemical Industry [source] Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheresPOLYMER INTERNATIONAL, Issue 5 2003Jin-Xia Huang Abstract Micron-size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1,5 µm were prepared by dispersion copolymerization in polar media with poly(N -vinylpyrrolidone)(PVP) as steric stabilizer, 2,2,-azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7,3.5 mol l,1, having a maximum of 5.01 µm at the concentration of 2.1 mol l,1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier-transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry [source] Blood cell separation using crosslinkable copolymers containing N,N -dimethylacrylamidePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 4 2007Shizue Hayashi Natori Abstract Amphiphilic copolymers using hydrophilic N,N -dimethylacrylamide (DMA), hydrophobic methyl methacrylate (MMA) and a crosslinkable monomer, 3-methacryloyloxypropyl trimethoxysilane (MTSi), were synthesized and evaluated as coating materials for leukocyte removal filters for whole blood. When filters composed of non-woven fabrics were coated with crosslinked synthesized copolymers, the elution ratios of the copolymers to water were adequately low because of the crosslinking with trimethoxysilane groups of MTSi units in the copolymers. Filters coated with crosslinked poly(DMA- co -MTSi) having a 0.96 mole fraction of DMA units showed a 0.35,±,0.44% platelet permeation ratio and a logarithmic reduction of 4.0,±,0.68 for leukocytes. On the other hand, an increase in the content of MMA units in the DMA-containing copolymers improved the permeation ratio of the platelets dramatically. Filters coated with crosslinked poly(DMA- co -MMA- co -MTSi) containing a 0.39 mole fraction of MMA units and a 0.58 mole fraction of DMA units showed an 86,±,3.0% platelet permeation ratio and a logarithmic reduction of 2.1,±,1.2 for leukocytes. This indicates that an adequate content of hydrophobic monomer units, such as MMA units, is necessary for effective platelet permeation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Solid polymer electrolytes I, preparation, characterization, and ionic conductivity of gelled polymer electrolytes based on novel crosslinked siloxane/poly(ethylene glycol) polymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Ping-Lin Kuo Abstract A series of crosslinked siloxane/poly(ethylene glycol) (Si,PEG) copolymers were synthesized from the reactive methoxy-functional silicone resin (Si resin) and PEGs with different molecular weights via two kinds of crosslinking reactions during an in situ curing stage. One of the crosslinking reactions is the self-condensation between two methoxy groups in the Si resin, and another one is an alkoxy-exchange reaction between the methoxy group in the Si resin and the OH group in PEG. The synthesized crosslinked copolymers were characterized by Fourier transform infrared spectroscopy, DSC, and 13C NMR. The crosslinked copolymers were stable in a moisture-free environment, but the SiOC linkages were hydrolyzed in humid conditions. The gel-like solid polymer electrolytes (SPEs) were prepared by impregnating these crosslinked Si,PEG copolymers in a propylene carbonate (LiClO4/PC) solution. The highest conductivity reached 2.4 × 10,4 S cm,1 at 25 °C and increased to 8.7 × 10,4 S cm,1 at 85 °C. The conductivities of these gel-type SPEs were affected by the content of LiClO4/PC, the molecular weights of PEGs, and the weight fraction of the Si resin. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2051,2059, 2004 [source] | ||||||||||