bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical polymerization of some monomers with schiff's base structure. A voltammetric study
Authors: Simionescu C. I. , Grovu‐Ivanoiu M. , Cianga I. , Grigoras M. , Duca A. , Cocârla I. 
Published: April 2003

AbstractThe electrochemical polymerization of some Schiff's base‐type monomers like pyrrole‐2‐aldehyde azine, N,N′‐di(2‐pyrrolylmethylene)‐1,4‐diaminobenzeneSystematic name: 2,2′‐[1,4‐phenylenebis(nitrilomethylidyne)]dipyrrole.
, and N,N′‐di(2‐pyrrolylmethylene)‐4,4′‐diaminobiphenylSystematic name: 2,2′‐[4,4′‐biphenylylenebis(nitrilomethylidyne)]dipyrrole.
proceeds as a precipitating polymerization to the anodic compartment. The voltammetric study of monomers and polymers using Pt electrodes and paste‐carbon electrodes were carried out. The results are in agreement with the MO calculations using the Hückel approximation for evaluating of the reactivity of the monomers.
Synthesis of a new macromonomeric peroxyinitiator having poly(tetrahydrofuran) Units
Authors: Savaskan Sevil , Hazer Baki 
Published: April 2003

AbstractA new macromonomeric peroxyinitiator (MMPI) was synthesized by the reaction of polytetrahydrofurandiol (p‐THF‐diol), Mw (1000), isophorone diisocyanate, 2,5‐dimethylhexyl‐2,5‐dihydroperoxide and 2‐isocyanatoethyl methacrylate. Homopolymerization of MMPI at 80°C gave crosslinked polytetrahydrofuran (poly‐THF) with swelling ratios in CHCl3 varying between 1.4 and 4.2.Styrene polymerization initiated by MMPI at 80°C in bulk gave crosslinked poly‐THF‐b‐polystyrene block copolymers. The overall rate constant, k, was found to be 1 · 10−4 (L mol−1)1/2 s−1 by keeping the polymer yield below 15%. Swelling ratios of the crosslinked block copolymers in CHCl3 were between 2.7 and 75 according to the concentration of MMPI and the polymerization time. In case the MMPI concentration was kept constant while the polymerization time was increased, swelling ratios were found between 3.55 and 7.07. Thermogravimetric analysis showed that the crosslinked block copolymers were still containing undecomposed peroxy groups, so they can thermally initiate styrene polymerization in order to obtain multicomponent cross‐linked copolymers.
Coating of carbon‐fiber surface by silicon carbide via sol‐gel mixtures of tetraethyl orthosilicate and phenolic resin
Authors: Tan Ton That Minh , Nieu Nguyen Huu , Tan Phan Minh , Thanh Nguyen Dac 
Published: April 2003

AbstractThe preparation of a SiC coating on a carbon fiber surface using a sol‐gel mixture of tetraethyl orthosilicat (TEOS) and phenolic resin was studied. FTIR and SEM investigations indicated that the SiC coating can be formed by carbothermal reduction of the sol‐gel mixture at 1420°C for 15–20 min in an argon atmosphere. TGA of the coated fiber was also performed, showing that the SiC coating improves the thermooxidative stability of the carbon fiber. With the thickness of the obtained coating of 0.47 μm using a C/Si ratio of 4, this treatment does not affect the carbon fiber strength.
Stereoselective polymerization of butadiene by a new dicationic nickel complex
Authors: Gerbase Annelise Engel , de Souza Roberto Fernando , de Souza Vichi Eduardo Joaquim , da Cunha Fernanda Vieira 
Published: April 2003

AbstractThe new dicationic nickel complex [dppfNi(MeCN)4][BF4]2 (dppf = 1,1′‐bis(diphenylphosphino)ferrocene) in the presence of diethylaluminium chloride (AIEt2CI) exhibited high activity on the 1,3‐butadiene polymerization. Reaction time, temperature and aluminium/nickel molar ratio were optimized in order to achieve maximum activity and selectivity. Conversions higher than 90% were obtained in contrast to other nickel‐based systems using phosphine ligands, the resulting polybutadiene showed high cis‐1,4 (<80%) content and only small amount of 1,2‐units (2%). All polymers presented low molecular weights (Mw > 11 800).
Initiation of polymerization with substituted ethanes, 16. End‐reactive methacrylate oligomers as precursors of block copolymers
Authors: Braun Dietrich , Steinhauer‐Beißer Susanne 
Published: April 2003

AbstractEnd‐reactive methacrylate oligomers, obtained by free‐radical polymerization of methyl, n‐butyl and tert‐butyl methacrylate with tetraphenylsuccinonitrile as initiator were used as free‐radical macroinitiators for the polymerization of styrene to prepare block copolymers. It could be shown by gel‐permeation chromatography coupled with FTIR spectroscopy that the oligomers are incorporated as segments in the block copolymers.The tert‐butyl ester groups of tert‐butyl methacrylate‐styrene block copolymers were hydrolysed and neutralized to yield amphiphilic polymers which were characterized by thermogravimetry and dynamic mechanical thermal analysis. The existence of an extended rubbery plateau proved that triblock ionomers had been obtained, due to termination by combination of growing styrene block radicals.
Structural changes in poly(methyl methacrylate) during deep‐etch X‐ray synchrotron radiation lithography. Part III: Mode of action of the developer
Authors: Schmalz Olaf , Hess Michael , Kosfeld Robert 
Published: April 2003

AbstractThe structural changes in poly(methyl methacrylate) (PMMA) caused by radiochemical reactions are predominantly governed by a decrease in molar mass and a splitting of side chains. It can be shown that the removal of the irradiated parts of PMMA is not a pure physical dissolving, but that there is a chemical reaction proceeding, the products of which are well soluble in polar solvents. This special type of reaction restricts this process on the irradiated areas and hence explains the high selectivity of the developing of the lithographic structures. Knowledge of these mechanisms leads to the prediction that isotactic PMMA shows an increased selectivity of the developing agent. Further improvements and optimizations of etching and developing are therefore possible.
Untersuchungen zur synthese von poly(butadien‐co‐propylenoxid) mit einem ziegler‐natta‐titankatalysatorsystem
Authors: Kaulbach Ralph , Gebauer Ulrich , Mähner Christian , Lechner Manfred D. , Gehrke Klaus 
Published: April 2003

AbstractFür die Copolymerisation von 1,3‐Butadien mit Propylenoxid wurde nach dem Vergleich der drei Katalysatorsysteme Nd(Oct)3/Al2Cl3ET3/Al(i‐But)3, Ni(Oct)2/ BF3OEt2/AlEt3 und Al(i‐But)3/I2/TiCl4 das Titankatalysatorsystem eingesetzt. Neben dem Einfluß der Monomerzusammensetzung auf den Umsatz, die Microstruktur, die Copolymerzusammensetzung, die Molmassen sowie die Molmassenverteilungen wurden auch die Polymerisationszeit und das Aluminium/Titan‐Verhältnis untersucht. Die Copolymerisationsparameter wurden nach Kelen‐Tüdős zu rButadien = 0,9 und rPropylenoxid = 3,9 bestimmt. Der Copolymernachweis erfolgte über 13C‐NMR‐Spektroskopie und Extraktionsuntersuchungen in Verbindung mit 1H‐NMR‐Spektroskopie.
Synthesis of flexible polyarylates by interfacial polycondensation. Part II: Incorporation of 4,4′‐thiodiphenol
Authors: Chen Tsu‐Hwei , Wang Ding‐Chang , Chiu Wen‐Yen , Chen Leo‐Wang 
Published: April 2003

AbstractThe toughness of polyarylates was improved by incorporation of 4,4′‐thiodiphenol and bisphenol A, being introduced in the aqueous phase of an interfacial polycondensation reaction. The modified polyarylates possessed slightly lower tensile strength and modulus but much higher Izod impact strength due to the flexibility of the incorporated segments. In addition, the superb thermal properties typical for polyarylates were reserved in the modified polyarylate, thus assuring its broad applicability for those applications where extremely stringent criteria of thermal characteristics are required.
Hydrogels for biomedical use based on 1‐vinyl‐2‐pyrrolidone crosslinked with macromonomers
Authors: Michálek Jiři , Vacík Jiři , Kúdelková Jana , Ježová Naděžda 
Published: April 2003

AbstractMacromonomers of various chain lengths with an average of three allyl double bonds per chain were prepared by anionic copolymerization of allyl methacrylate with methyl methacrylate. The macromonomers were characterized by gel permeation chromatography and nuclear magnetic resonance. The macromonomers were then copolymerized with 1‐vinyl‐2‐pyrrolidone to form three‐dimensional structures. Their optical, swelling and mechanical properties were studied and the crosslinking efficiency was determined. The copolymer properties are not greatly affected by macromonomer chain lengths up to 40‐mers; above 50‐mers there is a slight decrease in the equilibrium water content and a significant increase in the modulus of elasticity. The crosslinking efficiency depends on the macromonomer chain length; a marked increase was observed for the 50‐mer because of a greater number of methyl‐methyl interactions. Copolymers have favourable strength‐strain properties and a low content of water‐soluble extracts, in which the IR analysis demonstrated the presence of 1‐vinyl‐2‐pyrrolidone homopolymers. In spite of the good results obtained for all the macromonomers described in this work, the 50‐mer seems to be optimal for copolymerization with 1‐vinyl‐2‐pyrrolidone.
Graft polymerization of vinylidene chloride onto cellulose. A method to ascertain the grafting yield
Authors: Casinos Ismael , Gual Cristina 
Published: April 2003

AbstractThe graft polymerization of vinylidene chloride (VDC) onto cellulose initiated by ceric ions is reported. The grafting yield increases with reaction time and then levels off after 6 h. On the other hand, the grafting efficiency decreases rapidly from high initial values at short reaction times and then approaches to a constant value. The mechanism from of grafting is suggested for the present copolymerization. In order to determine both grafting yield and grafting efficiency, the separation of homopolymer and graft polymer is required. Sufficiently high temperatures are needed to dissolve poly(vinylidene chloride) (PVDC) because of its high crystallinity and melting point. Cyclohexanone dissolves the graft copolymer at 120°C bringing about some degradation of cellulose. Degradation is produced by hydrogen chloride formed throughout a slight dehydrochlorination of the synthetic polymer. A method inert for cellulose is suggested to retrieve the homopolymer from the polymerization crude by using a mixture of dry cyclohexanone and 4‐methylpyridine as solvent.
Elastic properties of thermosets in glassy state
Authors: Verdu J. , Tcharkhtchi A. 
Published: April 2003

AbstractThe Young's modulus E and Poisson's ratio v of various thermosets, including 6 amine crosslinked epoxies, one anhydride crosslinked epoxy, one styrene crosslinked polyester and one styrene crosslinked vinylester, were determined from tensile tests in the 220–393 K temperature range and 1.6710−4−1.6710−2 s−1 strain rate range. The bulk (B) and shear (G) modulus were calculated from E and v. Some observations about structure‐property relationships can be derived from these data and their comparison with corresponding ones relative to linear polymers. B appears to depend essentially of the cohesion and packing density and does not depend, practically, of temperature and strain rate. In contrast, G depends sharply of the local molecular mobility, this latter being affected by an antiplasticization mechanism. The Poisson's ratio seems to be systematically higher for thermosets than for linear polymers.
Monte‐carlo modelling of the formation, structure and properties of polymer networks
Authors: Dutton S. , Stepto R. F. T. , Taylor D. J. R. 
Published: April 2003

AbstractA new Monte Carlo (MC) algorithm is reported which enables RAfa +RBfb polymerisations to be simulated. It is based on the random reaction of pairs of groups for intermolecular reaction, with intramolecular reaction weighted according to Gaussian statistics and the size of ring structure being formed. The algorithm counts all the ring structures formed and enables polymerisations to be simulated efficiently up to complete reaction. Gel point and modulus results from trifunctional and tetrafunctional polyurethane‐forming polymerisations are modelled, with particular emphasis on the effects on modulus of network defects at complete reaction. More in keeping with experiment, higher reductions in modulus at complete reaction are predicted using the the present algorithm than using Biosym MC software. However, it is shown that quantitative agreement with experiment cannot be obtained unless relationships defining the entropies of various ring structures are elucidated and more accurate modelling of the chain statistics governing the intramolecular reaction forming ring structures of various sizes is used.
Synthesis and properties of epoxy‐episulfide resins
Authors: Bell J. P. , Don Trong‐Ming , Voong Senh , Fernandez A. , Ku W. 
Published: April 2003

AbstractStandard epoxy resins have good mechanical properties, but their prolonged low temperature curing time limits their potential use in clinical applications as well as in many industrial applications. A fast‐curing epoxy‐episulfide resin has been developed. The gel time of epoxy‐episulfide made from EPONTrade mark of Shell Chemical Company.
828 ranges from 2 to 10 minutes by changing the ratio of the ingredients. The heat of reaction of this system is low, resulting in low cure shrinkage. Water absorption of the episulfide network is low. The epoxy‐episulfide system cured with polyamide curing agent V‐40 exhibits two transition temperatures, at about 85°C and 130°C, as shown in dynamic mechanical analysis data. In order to solve the long term stability problem of the above episulfides, and also the mixing problem, a lower viscosity resin, Eponex, was used to make Eponex‐sulfide. Eponex‐sulfide systems show promise in that they remain in a stable liquid form without epoxy. The other advantages appear to be retained.
Molecular design of reactive microgels
Authors: Kaczun J. , Funke W. 
Published: April 2003

AbstractStructure and properties of microgels prepared by emulsion copolymerization depend on the composition and concentration of the monomers at the reaction sites, on the reactivity ratios and on the solubility of the comonomers in water. By separate and joint solubilization of 1,4‐divinyl benzene and various comonomers of different solubility it could be shown, that the diffusion control of the copolymerization rate is favoured by crosslinking, by a high concentration of an oil‐soluble initiator and of the emulsifier and by a low solubility of the comonomer in water.
Designing elastomer network for desired tire performance characteristics
Authors: Futamura Shingo 
Published: April 2003

AbstractRubber elasticity is associated with changes in configurational entropy of a long chain. Because the chain cannot change its configuration instantaneously, there is a time delay in deformation to an applied force. This delayed response is the source of viscoelasticity and hysteresis energy loss of elastomer networks. Many tire performance properties are related to the viscoelasticity of tire components. Wet and dry traction of tire is related to the energy loss of the tread material at very high frequencies. On the other hand, rolling resistance of tire is characterized by the energy loss of tread material at relatively low frequencies. The dynamic viscoelastic properties of elastomer network shows characteristic zones on a frequency scale. At very high frequencies the energy loss is controlled by the segmental motions of the polymer chain. At lower frequencies the energy loss is related to the longer range motions of the chain. A series of polymers was synthesized to study the effect of micro‐ and macro‐structure of the polymer on the viscoelastic properties of tread compounds and their tire performance properties. As expected from the theory, the wet traction of the tire was highly correlated to the segmental motions of the chains; namely, the glass transition temperature of the polymer. The energy loss of the compounds at a higher temperature, however, was related to the macrostructure of the polymer chain. Those examples illustrate that the fundamental understanding of the theory of elastomer network allows a tire engineer to obtain the best balance of tire performance characteristics.
Peripherally restraining type rubber bearing
Authors: Sasaki Teruo 
Published: April 2003

AbstractSeismic isolation was reconfirmed to be extremely efficient for the protection of buildings, and hence human life, on the occasion of the Great Hanshin Earthquake. Rubber bearings are placed under the buildings for isolation, and thus the type of rubber bearings is a dominant factor for efficient isolation. In this report, the performance of peripherally restraining type rubber bearing (PRB) was examined where its contracted model was found to simulate the performance of full scale PRB precisely. Damping ratio and vertical spring constant of PRB are as good as the existing ones. PRB showed lower critical shear strain, but it was concluded that no problems were found for the actual use of PRB.
Preparation and structural characteristics of stimuli‐responsive hydrogel microsphere
Authors: Nakazawa Yoshiyuki , Kamijo Yukiko , Fujimoto Keiji , Kawaguchi Haruma , Yuguchi Yoshiaki , Urakawa Hiroshi , Kajiwara Kanji 
Published: April 2003

AbstractMonodisperse hydrogel microspheres were prepared by precipitation polymerization from acrylamide (AAm), methylenebisacrylamide (MBAAm) and methacrylic acid (MAc) in ethanol, and examined their stimuli response by changing pH or temperature. The microsphere was found to contract continuously by heating. The microsphere with a lower‐content MBAAm exhibit more pronounced heat‐contraction. Also at low pH the microsphere contracted due to the protonation of the carboxyl group in MAc. The internal structure was observed by small angle X‐ray scattering (SAXS) and the stimuli‐response mechanism was discussed from the view of network chain conformation.
Elastic properties of real elastomers at small deformations
Authors: Takigawa Toshikazu , Urayama Kenji , Yamasaki Satoshi , Masuda Toshiro 
Published: April 2003

AbstractElastic properties of real elastomers were examined by using partial derivatives of the strain energy density function (W) with respect to the invariant (Ii, i=1,2,3) of deformation tensor. The values of the derivatives at zero strain limit for styrene‐butadiene rubber (SBR), nitrile‐butadiene rubber (NBR) and butadiene rubber (BR) were compared with those derived from the theory shown in the previous paper, where compressibility of the materials was taken into account. The asymptotic behavior of the derivatives for isoprene rubber (IR) and segmented polyurethaneurea (SPU) was also compared with those of the three types of rubbers. It was shown that the theoretical predictions for the limiting value agreed fairly well with the experimental values of the elastomers.
Network formation and swelling behavior of photosensitive poly(vinyl alcohol) gels prepared by photogenerated crosslinking
Authors: Shindo Yoichi , Katagiri Naoya , Ebisuno Toichi , Hasegawa Masatoshi , Mitsuda Miyuki 
Published: April 2003

AbstractPoly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular crosslinks are obtained.The proportion of the free water to the bound water in PVA‐SbQ gels was 3.3−2.9 despite of the large change in conversion of photodimerization of SbQ groups, x=0.27−0.58. The water uptake after swelling of the gels in water increased 6–27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, D, were (2.2−5.8) × 10−5 cm2 S−1 for a 88% saponified PVA with 1 . 3 mol% SbQ groups. The volume of the gel increased discontinuously about 10‐fold for the 99% saponified PVA with 0 . 096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.
Permeation and separation of organic liquid mixtures through liquid‐crystalline polymer networks
Authors: Inui Kuniaki , Miyata Takashi , Uragami Tadashi 
Published: April 2003

AbstractA side‐chain liquid‐crystalline polymer (LCP) was synthesized by the addition of the mesogenic monomer to poly(methyl siloxane) in presence of a Pt‐catalyst. When an aqueous solution of 10wt% ethanol was permeated through a LCP membrane by pervaporation at various temperatures, the permeation rate increased with increasing temperature and drastically changed at glass‐nematic (Tg) and nematic‐isotropic (TNI) transition temperatures of the LCP membrane. The LCP membrane exhibited the waterpermselectivity in the glassy and liquid‐crystalline states. The ethanol concentration in the permeate increased with increasing permeation temperature and the LCP membrane changed from the waterpermselectivity to the ethanol‐permselectivity around TNI. These results suggested that the permselectivity was influenced by the change of the LCP membrane structure, that is, its state transformation. It was found that a balance of the orientation of mesogenic groups and flexibility of siloxane chains is very important for the permeability and selectivity.
pH‐controlled uphill transport of ammonium ions through polymer membranes with sulfonic acid groups
Authors: Miyata Takashi , Tsutsui Kiyoko , Uragami Tadashi 
Published: April 2003

AbstractUphill transport of ammonium ions through a membrane with sulfonic acid groups were investigated with pH‐controllers which keep the solution at a constant pH. A membrane with sulfonic acid groups was prepared by casting an aqueous solution containing poly(styrenesulfonic acid) and poly(vinyl alcohol) on a glass plate. When a membrane with one side alkaline and the other acidic was fixed as a diaphragm in a cell, ammonium ions were transported from the alkaline side to the acidic side through the membrane against the concentration gradient of the adjacent solutions. Uphill transport of ammonium ions with pH‐controllers was more efficient than without, thus keeping the pH difference between both sides of the membrane constant, which is a driving force for the uphill transport. Furthermore, the effect of pH of the acidic side on the uphill transport was investigated and the mechanism of the pH‐controlled uphill transport is discussed.
Preparation of oxidized 6‐O‐glycolchitosan, pH sensitivity of its aqueous solution and of its cross‐linked hydrogel
Authors: Ohya Yuichi , Okawa Koji , Murata Jun‐ichi , Ouchi Tatsuro 
Published: April 2003

AbstractChitosan and 6‐O‐glycolchitosan, a water‐soluble chitosan derivative, were oxidized by periodate. In the case of chitosan, only degradation products were obtained. With 6‐O‐glycolchitosan, however, water‐soluble amphoteric polyelectrolyte derivatives of chitosan having higher molecular weight were obtained. The oxidized 6‐O‐glycolchitosan (OX‐GC) showed a pH sensitive change of viscosity in aqueous solution. Moreover, the OX‐GC hydrogel, cross‐linked with glutaraldehyde, showed a pH sensitive swelling behavior. The OX‐GC showed biodegradation behavior by lysozyme after acetylation.