bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of diblock and triblock copolymers containing dendrons via ‘living’ controlled radical polymerization
Authors: Zhao You‐Liang , Jiang Jing , Chen Chuan‐Fu , Xi Fu 
Published: December 2002

AbstractThe dendritic Fréchet‐type polyarylether 2‐bromoisobutyrates (Gn‐Br, n = 1–3) as macroinitiators for the ‘living’/controlled radical polymerization of styrene (St) and methyl methacrylate (MMA) were investigated. The atom transfer radical polymerization of St and MMA carried out with CuBr/bpy (2,2′‐bipyridine) catalyst in bulk yielded well‐defined dendritic–linear diblock copolymers (Gn–PSt and Gn–PMMA). The use of G3–PSt for the block copolymerization of MMA and G3–PMMA for the chain extension polymerization of MMA in the presence of CuBr/bpy catalyst is also described. The triblock copolymers obtained were of predetermined molecular weights and relatively low polydispersities, which indicates the living nature of the reaction system.© 2002 Society of Chemical Industry
Poly(ethylene‐co‐vinyl acetate)‐graft‐poly(methyl methacrylate) (EVA‐graft‐PMMA) as a modifier of epoxy resins
Authors: García Filiberto González , Soares Bluma G , Williams Roberto J J 
Published: December 2002

AbstractConventional approaches to toughen thermosets are: (1) the polymerization‐induced phase separation of a rubber or a thermoplastic, or (2) the use of a dispersion of preformed particles in the initial formulation. In the present study it is shown that it is possible to combine both techniques by using graft copolymers with one of the blocks being initially immiscible and the other that phase separates during polymerization. This is illustrated by the use of poly(ethylene‐co‐vinyl acetate)‐graft‐poly(methyl methacrylate) (EVA‐graft‐PMMA) as modifier of an epoxy resin. EVA is initially immiscible and PMMA phase separates during polymerization. Blends of an epoxy monomer based on diglycidylether of bisphenol A (DGEBA, 100 parts by weight), piperidine (5 parts by weight), and PMMA (5 parts by weight), showed the typical polymerization‐induced phase separation of PMMA‐rich domains before gelation of the epoxy network. Replacing PMMA by EVA‐graft‐PMMA (5 parts by weight), yielded stable dispersions of EVA blocks, favoured by the initial solubility of PMMA blocks. Phase separation of PMMA blocks in the course of polymerization led to a dispersion of in situ generated biphasic particles (plausibly composed of EVA cores surrounded by PMMA shells), with average diameters varying from 0.3 to 0.6 µm with the cure temperature. This procedure may be used to generate stable dispersions of biphasic particles for toughening purposes.© 2002 Society of Chemical Industry
Preparation and characterization of star polymers with polyurethane cores using polycaprolactone triol
Authors: Wang Tzong‐Liu , Huang Fang‐Jung , Lee Swu‐Wen 
Published: December 2002

AbstractStar‐shaped polymers with two different core sizes were prepared by step polymerization. Their structures were confirmed by FTIR and 1H NMR studies. X‐ray diffraction studies showed highly crystallized patterns for this type of star polymer. Thermogravimetric analysis curves displayed an excellent thermal stability and a two‐step degradation mechanism for these materials. In addition, it indicated that if the length of the triol segment were longer, the degradation temperature at 10% weight loss would be higher.© 2002 Society of Chemical Industry
Characterization of cure reactions of anhydride/epoxy/polyetherimide blends
Authors: Kim Minyoung , Kim Wonho , Choe Youngson , Park Joung‐Man , Park In‐Seo 
Published: December 2002

AbstractThe cure kinetics of blends of epoxy (diglycidyl ether of bisphenol A)/anhydride (nadic methyl anhydride) resin with polyetherimide (PEI) were studied using differential scanning calorimetry under isothermal conditions to determine the reaction parameters such as activation energy and reaction constants. By increasing the amount of PEI in the blends, the final cure conversion was decreased. Lower values of final cure conversions in the epoxy/PEI blends indicate that PEI hinders the cure reaction between the epoxy and the curing agent. The value of the reaction order, m, for the initial autocatalytic reaction was not affected by blending PEI with epoxy resin, and the value was approximately 1.0. The value of n for the nth order component in the autocatalytic analysis was increased by increasing the amount of PEI in the blends, and the value increased from 1.6 to 4.0. A diffusion‐controlled reaction was observed as the cure conversion increased and the rate equation was successfully analyzed by incorporating the diffusion control term for the epoxy/anhydride/PEI blends. Complete miscibility was observed in the uncured blends of epoxy/PEI at elevated temperatures up to 120 °C, but phase separations occurred in the early stages of the curing process.© 2002 Society of Chemical Industry
Biologically active polymer: controlled‐release formulations based on Hymexazol
Authors: Tai Limin , Liu Dongxue , Shen Yongjia , Si Naiguo 
Published: December 2002

Abstract3‐(2‐Hydroxyethoxy)‐5‐methylisoxazole (2) was prepared by the reaction of 3‐hydroxy‐5‐methylisoxazole (1) with 2‐ethylene chlorohydrin. It reacted with methacryloyl chloride to afford 2‐[3‐(5‐methylisoxazolyl)oxy]ethyl methacrylate (4). The compounds 2 and 4 were confirmed structurally by IR, MASS and 1H NMR spectroscopy and MS. The fungicidal effects of 2 and 4 were investigated. Compound 4 was subjected to radical copolymerization with acrylamide and formed a copolymer 5. It would release the active agent 2 in a reasonable amount by a hydrolysis process. The release rates of the compound 2 were determined by high performance liquid chromatography (HPLC) under different pH conditions. The results indicate that the copolymer 5 is potentially useful for the development of the chemically controlled‐released formulations of Hymexazol.© 2002 Society of Chemical Industry
Near infrared (NIR) spectroscopy compared with thermogravimetric analysis as a tool for on‐line prediction of water diffusion in polyamide 6,6
Authors: Camacho Walker , Hedenqvist M S , Karlsson Sigbritt 
Published: December 2002

AbstractNIR spectroscopy in the transmission mode and thermogravimetric analysis were used to predict diffusion of water into polyamide 6,6 samples immersed in water at 40, 60, 75 and 90 °C for different periods of time. The sorption curves between 40 and 75 were sigmoidal indicating that the surface concentration was time dependent. The sorption curves were readily fitted by the use of a time‐dependent surface concentration and a water‐concentration‐dependent diffusivity. The zero‐concentration water diffusivity decreased non‐linearly and the activation energy of diffusion increased from 24 to 58 kJ mol−1, with decreasing temperature. The surface concentration relaxation time decreased rapidly. The sorption of water in thick polyamide samples was readily characterized by FT‐NIR spectroscopy. The accuracy and feasibility of this method was similar to conventional thermogravimetric methods. The greatest advantage of FT‐NIR, however, is the possibility of detecting and monitoring the moisture concentration on‐line and in a non‐destructive way.© 2002 Society of Chemical Industry
Polypyrrole/polyaniline conductive films obtained electrochemically on polycarbonate‐coated platinum electrodes
Authors: Karakışla Meral , Aksu Levent , Saçak Mehmet 
Published: December 2002

AbstractIn this study, two‐component free‐standing films were obtained by coating a polycarbonate (PC)‐coated Pt electrode first with polypyrrole (PPy) in an organic medium and then polyaniline (PAn) in an aqueous medium using an electrochemical technique. The amount of PPy and PAn contained in the films was controlled by varying the electrolysis time. The PC/PPy/PAn films were characterized by cyclic voltammetry, conductivity, FTIR and UV–visible spectrophotometry, and thermogravimetric analysis. The resistance change of the films was determined in the temperature range of −15 to 120 °C and their temperature sensor properties were investigated.© 2002 Society of Chemical Industry
Effect of surface treatment on the impact behaviour of fly‐ash filled polymer composites
Authors: Kishore  , Kulkarni S M , Sunil D , Sharathchandra S 
Published: December 2002

AbstractThe impact behaviour of epoxy specimens containing 10% by volume of fly‐ash particles with their surface treated for improving or decreasing adhesion is studied. The resulting behavioural patterns are listed and compared to those of composites containing untreated fly‐ash particles and unreinforced (ie neat) epoxy. It was noticed that samples involving adhesion‐increasing (ie acetone and silane) treatments show greater absorption of energy and maximum load compared to untreated samples and those subjected to adhesion‐reducing treatments. Ductility index, however, showed a reversed trend with adhesion‐reducing treatment yielding the highest value. In contrast, the energy absorbed was highest for neat resin and lowest for oil surface bearing ash particulate composites. Scanning electron microscope examination of the failed samples was carried out to obtain information on the fracture features with the aim of correlating microstructure to impact response. Thus, the higher ductility indices cases are shown to be distinct and different from composites containing other surface treatments for fillers.© 2002 Society of Chemical Industry
Melt strength of calcium carbonate filled polypropylene melts
Authors: Kao Nhol , Chandra Arnab , Bhattacharya Sati 
Published: December 2002

AbstractThis paper investigates the extensional rheology (through melt strength measurement) of calcium carbonate (CaCO3) filled polypropylene (PP) melts. Different concentrations of CaCO3 filled PP were produced by mixing two master batches of pure PP and 70 wt% CaCO3 filled PP in required proportions in a counter‐rotating twin‐screw extruder. It was found that the melt strength of the CaCO3–PP melts was independent of CaCO3 concentrations up to 25 vol%. Further increase in CaCO3 concentration led to a severe reduction of melt strength.© 2002 Society of Chemical Industry
Properties of hydrogels of atactic poly(vinyl alcohol)/NaCl/H2O system and their application to drug release
Authors: Shaheen Sharif Mohammad , Ukai Kohsuke , Dai Lixing , Yamaura Kazuo 
Published: December 2002

AbstractIn order to prepare cost‐effective physically cross‐linked hydrogels including food salt sodium chloride, samples, were prepared with various concentrations of NaCl and respective atactic poly(vinyl alcohol) (a‐PVA), and were evaluated. It had been observed that hydrogels containing NaCl concentration (9–11 wt%) along with a‐PVA concentration 9–5% respectively exhibited higher melting points (91.5–95.1 °C). A higher melting point characterizes the hydrogel composition of a system like a‐PVA(7%)/NaCl(11%)/H2O. The swelling degree of this hydrogel was found to be comparatively better at 37 °C than at any other temperature studied here. However, irregular Fickian swelling was found at this temperature. The UV light absorption maximum at 362–364 nm and minimum at 351 nm for this hydrogel had been found as evidence of physical cross‐linking. A drug, theophylline was loaded by solvent‐sorption and feed‐mixture dissolving methods. The feed‐mixture dissolving method is better than solvent sorption because of high drug loading, comparatively low fraction release rate and more sustained‐release of drug than that of solvent‐sorption. Theophylline was released twice as fast from the hydrogel after solvent‐sorption drug loading (3 h) than from that which used the feed‐mixture dissolving method (6.5 h). Theophylline‐loaded hydrogels of this system (feed‐mixture dissolving) were then prepared at high temperature (60 °C) thawing for 6 h followed by chilling at 0.4 °C for 3 h as one cycle. And the drug release behaviour and mass transfer were found almost the same as for chilling (24 h at 0.4 °C)–thawing (48 h at room temperature). Drug release behaviour was studied as apparently irregular Fickian diffusion (Higuchi Matrix Dissolution Model).© 2002 Society of Chemical Industry
Synthesis of hydrogel for drug delivery studies utilizing photoinitiator‐free photopolymerization based on the donor/acceptor pair, N‐vinylpyrrolidinone and hydroxypentyl maleimide
Authors: Ng Loo‐Teck , Jönsson Sonny , Swami Salesh , Lindgren Karin 
Published: December 2002

AbstractPhoto‐differential scanning calorimetry (photo‐DSC) was used to study the rate of photoinitiator‐free copolymerization of a donor/acceptor pair involving N‐vinylpyrrolidinone (NVP), and a water‐soluble N‐substituted maleimide, hydroxypentyl maleimide (HPMI). Glucose, 1,1‐diethoxy ethane (DEE) and isopropyl alcohol (IPA) were included for the evaluation of their efficiencies as hydrogen donors, and glucose was shown to be the most efficient in enhancing the rate of polymerization. This photoinitiator (PI)‐free system was extended to hydrogel preparation using the radiation method with UV as the radiation source based on the same donor/acceptor pair, ie NVP/HPMI, in the presence of glucose as the hydrogen donor. Swelling and drug release tests showed that this hydrogel exhibited high swelling ability and a rather fast drug release rate when using theophylline as the model drug. These tests also revealed that the drug release kinetics and the water diffusion into this hydrogel did not adhere to the Fickian model. Cytotoxicity testing showed no evidence of this hydrogel being cytotoxic.© 2002 Society of Chemical Industry
Synthesis and characterization of poly(N‐vinyl imidazole) hydrogels crosslinked by gamma irradiation
Authors: Pekel Nursel , Güven Olgun 
Published: December 2002

AbstractCrosslinked poly(N‐vinyl imidazole) (PVIm) hydrogels in the form of rods have been prepared by 60Co γ‐radiation initiated simultaneous polymerization and crosslinking of N‐vinyl imidazole in bulk and water. In binary aqueous systems, the percentage gelation decreased with increasing water content. The PVIm hydrogels synthesized were further protonated in HCl solutions of different concentration. PVIm and protonated PVIm (H‐PVIm) hydrogels have been characterized using spectroscopic and thermal methods, and the swelling behaviour of these two types of hydrogel has been investigated. PVIm hydrogels originally swelled to 600% (by volume) but in their protonated form at pH 7.0 reached 4000% swelling.© 2002 Society of Chemical Industry
Effect of polymer characteristics on Beckmann rearrangement of polymer supported ketoximes
Authors: Baby Shiney , Devaky K S 
Published: December 2002

AbstractBeckmann rearrangement has been carried out in polymeric oximes synthesised from rigid styrene–divinylbenzene copolymer and flexible styrene–hexanediol diacrylate (HDODA) copolymer. Oxime functions were incorporated into these polymers through a series of polymer‐analogous reactions. First the polymers were subjected to Friedel‐Crafts acylation reactions with low molecular weight acid chlorides to give a set of polymeric ketones. These polymeric ketones were converted to oximes by treating with hydroxylamine hydrochloride in the presence of pyridine. The oximes were subjected to rearrangement under acidic conditions into substituted amides. The polymeric amides obtained were characterised by IR spectroscopy and chemical degradative analysis. The rearrangement in the macromolecular matrices were found to follow the same mechanistic path as in the low molecular weight analogues. The rate of rearrangement was found to be faster in the HDODA crosslinked polystyrene system.© 2002 Society of Chemical Industry
Morphology of poly(butyl acrylate)/poly(styrene‐co‐methyl methacrylate) latex prepared by starved emulsion polymerization: II. Development of particle morphology
Authors: Huo Dongxia , Liu Dazhuang , Sun Peiqin 
Published: December 2002

AbstractHeterogeneous latexes were prepared by a two‐stage seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second‐stage polymer was poly(styrene‐co‐methyl methacrylate). By varying the amount of methyl methacrylate (MMA) in the second‐stage copolymer, the polarity of the copolymer phase could be controlled. It was found that the latex particles displayed different morphologies depending on the monomer ratio. The amount of MMA had a significant effect on the evolution of morphology. The morphologies were observed by transmission electron microscopy. In addition, the evolution of the particle morphology was predicted by the mathmatical model for cluster migration. The model gave the same trends as the experimental results.© 2002 Society of Chemical Industry
Curing kinetics and thermal property characterization of the bisphenol‐F epoxy resin and phthalic anhydride system
Authors: Gao Jungang , Zhao Hongchi , Li Yanfang 
Published: December 2002

AbstractThe curing kinetics of bisphenol‐F epoxy resin (BPFER) and curing agent phthalic anhydride, with N,N‐dimethylbenzylamine as an accelerator, were studied by differential scanning calorimetry (DSC). Analysis of DSC data indicated autocatalytic behaviour in the first stages of the cure for the system, and that this, could be well described by the model proposed by Kamal, which includes two rate constants, k1 and k2, and two reaction orders, m and n. The curing reaction in the later stages was practically diffusion‐controlled. To consider the diffusion effect more precisely, a diffusion factor, 𝒻(α), was introduced into Kamal's equation. The glass transition temperatures (Tgs) of the BPFER/phthalic anhydride samples were determined by means of torsional braid analysis. The thermal degradation kinetics of cured BPFER were investigated by thermogravimetric analysis.© 2002 Society of Chemical Industry
Particle nucleation and growth mechanisms in miniemulsion polymerization of styrene
Authors: Chern Chorng‐Shyan , Chang Hung‐Te 
Published: December 2002

AbstractStyrene miniemulsion polymerizations stabilized by sodium lauryl sulfate in combination with a reactive costabilizer, lauryl methacrylate (LMA) or stearyl methacrylate (SMA), were studied. A small amount of extremely hydrophobic dye was incorporated into monomer droplets (102 nm in diameter) to investigate particle nucleation and growth mechanisms. In addition to monomer droplet nucleation, particle nuclei generated in the aqueous phase (homogeneous nucleation) also play an important role in both LMA‐ and SMA‐containing polymerization systems. The way that these two nucleation mechanisms compete with each other is closely related to the water solubility of the costabilizer (LMA > SMA). The fraction of latex particles originating from homogeneous nucleation increases with decreasing hydrophobicity of the costabilizer. Zeta potential data of latex particles and the molecular weight and molecular weight distribution of emulsion polymers provide supporting evidence for the proposed competitive particle nucleation and growth mechanisms.© 2002 Society of Chemical Industry
Study on the microstructures and mechanical behaviour of compatibilized polypropylene/polyamide‐6 blends
Authors: Zeng N , Bai S L , G'Sell C , Hiver J‐M , Mai Y W 
Published: December 2002

AbstractA series of blends of polypropylene (PP)–polyamide‐6 (PA6) with either reactive polyethylene–octene elastomer (POE) grafted with maleic anhydride (POE‐g‐MA) or with maleated PP (PP‐g‐MA) as compatibilizers were prepared. The microstructures and mechanical properties of the blends were investigated by means of tensile and impact testing and by scanning electron microscopy and transmission electron microscopy. The results indicated that the miscibility of PP–PA6 blends was improved with the addition of POE‐g‐MA and PP‐g‐MA. For the PP/PA6/POE‐g‐MA system, an elastic interfacial POE layer was formed around PA6 particles and the dispersed POE phases were also observed in the PP matrix. Its Izod impact strength was four times that of pure PP matrix, whilst the tensile strength and Young's modulus were almost unchanged. The greatest tensile strength was obtained for PP/PA6/PP‐g‐MA blend, but its Izod impact strength was reduced in comparison with the pure PP matrix.© 2002 Society of Chemical Industry
Dielectric relaxation behaviour of poly(cyclobutyl methacrylate)s
Authors: Díaz‐Calleja Ricardo , García‐Bernabé Abel , Sánchez‐Martínez Enrique , Hormazábal Andrea , Gargallo Ligia , Radić Deodato 
Published: December 2002

AbstractDielectric behaviour of two poly(methacrylate)s with cyclobutyl groups in the side‐chains has been studied. This investigation was performed by determining the dielectric permittivity and loss in terms of frequency and temperature for poly(cyclobutyl methacrylate) (PCBuM) and poly(cyclobutylmethyl methacrylate) (PCBuMM). Dynamic dielectric measurements show sub‐glass relaxations, probably due to motions in the lateral chain, including the cyclobutyl ring. The effect of the insertion of a flexible spacer group into the side‐chain is also analyzed. The α relaxations were analyzed in terms of the Havriliak–Negami equation and the free volume theory tested according to the Vogel–Fulcher–Tamman–Hesse equation. The conductive and interfacial phenomena were studied by hopping and MacDonald–Coelho models.© 2002 Society of Chemical Industry
Atom force microscopic characterisation of the interaction forces between bovine serum albumin and cross‐linked alkylated chitosan membranes in media of different pH
Authors: Liu Wen Guang , Li Fang , Zhao Xiao Dong , Yao Kang De , Liu Qing Gang 
Published: December 2002

AbstractButyl, octyl and hexadecyl moieties were introduced into chitosan. The adhesion of bovine serum albumin (BSA) onto glucose aldehyde‐crosslinked alkylated chitosan membranes in pH media was investigated by probing the force‐displacement curves with BSA‐coated Atom force microscope (AFM) tips. The results indicated that, at the isoelectric point (IP), the sample membranes exhibited higher adhesion forces; and deviating from IP ie at pH 2, pH 6, the adhesion forces decreased. The adhesion forces at pH 2 are less than those at pH 6 due to the presence of electrostatic repulsive and attractive interactions, respectively. Measurements of the adhesion force confirmed quantitatively that the introduction of hydrophobic side‐chains to chitosan can facilitate protein adsorption; however, longer flexible side‐chains can depress protein adsorption to a certain degree. From an analyses of the adhesion forces, it is proposed that protein adsorption can be tuned by adjusting the lengths of the introduced side‐alkyl moieties.© 2002 Society of Chemical Industry
Biodegradable hollow fibres containing drug‐loaded nanoparticles as controlled release systems
Authors: Polacco Giovanni , Cascone Maria Grazia , Lazzeri Luigi , Ferrara Stefania , Giusti Paolo 
Published: December 2002

AbstractA ‘multiple’ delivery system was studied, consisting of hollow microfibres containing drug‐loaded nanoparticles. Both fibres and nanoparticles are made of biodegradable polymers, so that the system does not need any surgical operation to be removed. The main advantage of the system is that it allows the contemporaneous release of different kinds of drugs. Copolymers of poly(lactic acid) and ϵ‐caprolactone were used for the preparation of the fibres through both wet and dry–wet spinning procedures. Two types of nanoparticles, gelatin and poly(DL‐lactide‐co‐glycolide) nanoparticles, were prepared by simple water‐in‐oil and oil‐in‐water emulsions, respectively. Drugs such as dexamethasone and methotrexate were used to load the particles. The technique employed for the preparation of the nanoparticles filled fibres was described and the drug release characteristics of this system were investigated and compared with those of the free nanoparticles.© 2002 Society of Chemical Industry