bluuebunny/crossref_metadata_2025_split huggingface dataset:
Two‐dimensional artificial extracellular matrix: Bioadhesive peptide‐immobilized surface design
Authors: Kondoh Akihiro , Makino Keisuke , Matsuda Takehisa 
Published: April 2003

AbstractA novel artificial extracellular matrix derivatized with a cell adhesive peptide, Arg—Gly—Asp—Ser (RGDS) tetrapeptide, which is the central peptidyl sequence of the adhesive site of fibronectin, was designed. RGDS coupling was achieved via isocyanation of surface hydroxyl groups of poly(vinyl alcohol) (PVA) film and subsequent conversion to activated ester. The surface‐modified PVA film was quantitatively analyzed by ESCA. The surface density of RGDS was partly controlled by the degree of isocyanation of the PVA film. Bovine endothelial cells (ECs) adhered and grew well on the RGDS‐derivatized PVA film, irrespective of the presence or absence of the serum. The adhesion and growth of ECs were enhanced with an increase in the surface density of RGDS. When a sufficient amount of RGDS was added to the medium, the adhered ECs were delaminated. This indicated that the adhesion of ECs on an RGDS‐derivatized PVA surface is mediated by the RGD—ligand/receptor interaction. Thus, a peptidyl artificial matrix via surface derivatization was developed. © 1993 John Wiley & Sons, Inc.
The influence of the surface cross‐linking of the high‐density polyethylene induced by plasma treatment on the durability of treatment efficiency
Authors: Yao Yaoguang , Liu Xeushu , Zhu Yufen 
Published: April 2003

AbstractThe structure of the surface cross‐linking layer of high‐density polyethylene (HDPE) produced by plasma treatment was studied by DSC, X‐ray diffraction, elemental analysis, and infrared analysis. The relationship between the cross‐linking and the durability of the modification efficiency provided by the plasma treatment was investigated. The results of the structure analysis indicated that the polar groups introduced by the plasma just locate on the upper surface of the cross‐linking layer and the chemical constitution and structure of the inner part of the cross‐linking layer is similar to that of the uncross‐linking HDPE. The cross‐linking density of the gel decreases from the surface to the inside with a large gradient and the average cross‐linking degree of the whole gel is rather low. Nevertheless, the experiment proved that this cross‐linking layer can limit the mobility of the molecules in the cross‐linking layer and hinder the decay of the treatment efficiency significantly. When the surface cross‐linking induced by plasma reaches a certain extent, the treatment efficiency will remain relatively constant in storage. © 1993 John Wiley & Sons, Inc.
Gas transport properties of poly(3‐hydroxyoxetane)
Authors: Aguilar‐Vega M. , Paul D. R. , Vandenberg E. J. , Mullis J. C. 
Published: April 2003

AbstractGas transport properties for poly(3‐hydroxyoxetane) (PHO) were measured for five gases at 35°C. While PHO has very low gas permeability coefficients, they are larger than those reported for polyacrylonitrile (PAN), poly(vinyl alcohol) (PVA1) and copolymers of ethylene / vinyl alcohol (EVAL) for all gases tested except He. The permeability coefficients for PHO and EVAL are well correlated with the density of hydroxyl groups along the chain. Extrapolations to PVA1 give values that agree well with those estimated by Salame using the Permachor method. It is suggested that some of the reported experimental values for PVA1 are in error. © 1993 John Wiley & Sons, Inc.
Structure of the epoxy–chelate metal‐containing matrices: Theoretical aspects
Authors: Kurnoskin A. V. 
Published: April 2003

AbstractA theoretical analysis has been carried out of the structure of metalliferous epoxy–chelate polymers (MECP) based on diglycidyl ether of bisphenol‐A (DGEBA) hardened with metal complexes of the formula [M(L)n(X)p], where M is the cation of the transition metal; R, a nitrogen‐containing ligand; X, the anion of an organic acid; n, the number of the ligands in the complex molecule (n = 1 or 2), and p, the metal valency (p = 2 or 3). On the basis of the correlations between the tensile strength (σt) and tensile modulus (Et), and flexural strength (σf) and flexural modulus (Ef), of MECP, σt = f(Et)and σf = f(Ef), and supposing that when the condition \documentclass{article}\pagestyle{empty}\begin{document}$ \sigma _{_{t_A } }= \sigma _{_{t_B } } ,{\rm}\sigma _{_{f_A } }= \sigma _{f_B } ,{\rm}E_{t_A }= E_{t_B } ,{\rm}E_{f_A }= E_{f_B } $\end{document} is fulfilled, where A and B are complex hardeners of different structures but of the same class, the epoxy–chelate matrices have similar structures. The influence of the structural fragments of the hardener molecule (the metal, ligand, and anion) on the polymer properties was evaluated and it was found out that the biggest contribution to these properties belongs to the metal, the alteration of which changes the thermal stability (ΔM is the polymer mass loss after thermal treatment in air), deformability (ε), σf, Ef, and deflection temperature (DT) significantly. By this, the effect of the hardener structure change on the alteration of the MECP properties is maximal for ΔM, is minimal for the compressive strength (σc), and decreases in the series: ΔM > ε > DT > σf > Ef > σc. The type of the anion affects σc significantly, but the ligand type contributes the least to the polymer properties. The obtained dependencies of the MECP properties on the structural fragments of the complex hardeners allow preliminary evaluation of the structure of the chelates and epoxy–chelate compositions necessary to produce epoxy polymers with required properties. The new method of the theoretical investigation of the effect of the structural fragments (method of TIESF) of the polymer matrix on the polymer properties can be used to analyze the structures of the polymers of other classes and to predict the optimal structures, promising the production of the materials with the optimal properties. © 1993 John Wiley & Sons, Inc.
Silane cross‐linking of PVC. I. Grafting of mercaptoalkylalkoxysilanes onto PVC: Properties of the grafted and cross‐linked product
Authors: Kelnar I. , Schätz M. 
Published: April 2003

AbstractThe reaction of poly(vinyl chloride) (PVC) with mercaptoalkyltrialkoxysilanes yielded silane‐grafted PVC that can be cross‐linked by the hydrolytic mechanism. The grafting of the silanes on the plasticized and unplasticized PVC was carried out at 180° C during processing in the presence of basic lead‐containing stabilizers. The reaction is favorably affected by the presence of plasticizers and lubricants containing polar, preferably ester, groups. The silane‐grafted and cross‐linked polymers have satisfactory thermal stability. The results of strength measurements at elevated temperatures after cross‐linking by water indicate that the material obtained has greatly improved parameters that are suitable for a number of applications. © 1993 John Wiley & Sons, Inc.
Synthesis and characterization of poly(ether urethane)‐nylon 6 block copolymer
Authors: Seo Seung Won , Ha Wan Shik 
Published: April 2003

Abstractpoly(ether urethane) (PEU) prepolymer terminated with isocyanate at both ends was prepared by controlling the mol ratio of poly(tetramethylene glycol) and methane diphenyl‐4,4'‐diisocyanate. Using this prepolymer as an activator, the anionic polymerization of ϵ‐ caprolactam was carried out to obtain PEU‐nylon 6 block copolymer. The phase structure of the block copolymers was characterized on the basis of molecular interaction. The results of dynamic mechanical and thermal analyses revealed that the block copolymer films prepared via melt pressing and subsequent quenching had a one‐phase structure. The equilibrium melting temperatures determined by a Hoffman‐Weeks plot showed that the two blocks are miscible in the melt state. N‐Trifluoroacetylation of the block copolymer led to the conclusion that this miscible behavior is due mainly to the specific interaction between urethane groups in PEU block and amide groups in nylon 6 block through hydrogen bonding. © 1993 John Wiley & Sons, Inc.
Reactive extrusion of styrene polymers
Authors: Michaeli W. , Höcker H. , Berghaus U. , Frings W. 
Published: April 2003

AbstractReactive extrusion is the term used to denote a plastics processing method in which an extruder is used as a reactor for the continuous synthesis and modification of polymers. This paper describes the manufacture of polystyrene and styrene‐isoprene copolymers by a reactive extrusion process: anionic “living” s‐butyllithium‐initiated bulk polymerization was performed in a co‐rotating closely intermeshing twin‐screw extruder. The results of the process analysis show that living polymerization of styrene can be performed in a screwtype reactor, despite the high reaction temperatures of over 200°C. The polystyrene melt can be modified in bulk with comonomers or coupling reagents immediately after polymer synthesis. Depending on the raw material, formulation, and process parameters, the process variants developed and analyzed at the Institut für Kunststoffverarbeitung for homopolymerization of styrene, copolymerization of styrene‐isoprene mixtures, and sequential polymerization of styrene and isoprene resulted in styrene polymers with widely differing structural characteristics and properties. For example, the copolymerization of styrene‐isoprene monomer mixtures produced poly [isoprene‐co‐styrene)‐b‐styrene]. The sequential polymerization of styrene and isoprene led to poly(styrene‐b‐isoprene) contaminated with partly cross‐linked low molecular weight polyisoprene. The polyisoprene content is presumably formed by side reactions due to the high reaction temperatures. © 1993 John Wiley & Sons, Inc.
Crosslinking of HDPE during reactive extrusion: Rheology, thermal, and mechanical properties
Authors: Kim K. J. , Kim B. K. 
Published: April 2003

AbstractThe effect of peroxide and coagent, alone and together, on the crosslinking of HDPE during melt extrusion was studied. The melt flow index decreased rapidly with peroxide (1,3‐bis (t‐butylperoxy‐isopropyl) benzene), and smoothly with trimethylolpropanetriacrylate (TMPTA), but showed a small increase with parabenzoquinone (PBQ).Melt viscosity of 0.3 phr peroxide‐treated PE responded elastically, whereas that of 0.3 phr TMPTA showed yield behavior. Tm (crystalline melting temperature) and Tc (crystallization temperature) increased with peroxide, Tm decreased, and Tc increased with TMPTA. ΔHf (heat of fusion) increased at 0.05 phr followed by a sharp drop, more with peroxide and less with TMPTA. Hardness and preyield properties increased with TMPTA, and peroxide (except hardness) with the loss of elongation at break. The most significant improvement was obtained with impact strength, over 5 times with peroxide and 7 times with TMPTA.When the TMPTA was used in combination with peroxide, more redution in MI, followed by a further increase of hardness, modulus, and strength, was obtained, but impact strength was decreased below that of TMPTA alone. © 1993 John Wiley & Sons, Inc.
Influence of the experimental conditions on the photooxidation of poly(vinyl chloride)
Authors: Gardette J. L. , Gaumet S. , Philippart J. L. 
Published: April 2003

AbstractThe photooxidation of poly(vinyl chloride) involves complex reactions in which photooxidation and photodiscoloration by the formation of polyenes compete. These reactions are now fairly well understood, and on the basis of the mechanisms formerly reported, it appears possible to investigate the influence of irradiation parameters such as the thickness of the samples, the temperature, or the external pressure of oxygen. This objective requires the distribution of the photoproducts through the irradiated polymer matrix to be analyzed at the microscopic level. The shapes of the profiles that are determined show that the overall behavior of the polymer results from oxygen‐starvation effects. The diffusion of oxygen controls the rate of the photooxidation of the matrix, the rate of the photooxidative bleaching of the polyenes, and the rate of absorption of the light by the residual polyenes that have not been oxidized. © 1993 John Wiley & Sons, Inc.
In situ modification of microporous membranes
Authors: Gabriel E. M. , Gillberg G. E. 
Published: April 2003

AbstractUnder proper conditions, in situ polymerizations of acrylic acid monomer solutions were performed within the microporous structures of a hydrophobic membrane, Celgard ® 2500. poly(acrylic acid) modified pores have been characterized to be permanently wettable by aqueous solutions, to be capable of gelling water to withstand increased transmembrane pressure gradients, and also to possess a higher transmembrane electrical resistance. In cases of less concentrated acrylic acid monomer solutions, a cross‐linker was employed to facilitate polymer permanency within the infrastructure of the hydrophobic membranes. © 1993 John Wiley & Sons, Inc.
Concentration and separation of metallic ions from aqueous solutions by using EC‐PEG 4000 alloy membranes
Authors: Solpan D. , Sahan M. 
Published: April 2003

AbstractThe concentration and separation of some metallic ions have been achieved by complexing these species with suitable macromolecules or with water‐soluble polymers in ultrafiltration. The effect of water‐soluble poly(vinyl alcohol) (PVA) on the concentration and separation of Cu2+, Ni2+, and Fe3+ ions have been investigated by using EC‐PEG4000 alloy membranes in ultrafiltration experiments. The water permeability of the membranes has been measured at various pressures. The permeability of these membranes for metal ions, however, has been recorded at constant pressure but at different pH values. The highest water‐permeable membrane is also permeable for Cu2+ and Ni2+, but it shows a considerable retention for Fe3+, probably as a result of the hydrolysis of Fe3+. The retentions of metallic ions and metallic ion‐PVA couples have been determined at constant pressure but varying pH and polymer concentration values. It has been shown that Fe3+/Ni2+ pairs can well be separated by using PVA. © 1993 John Wiley & Sons, Inc.
Thermal and mechanical properties of copolymers of methyl methacrylate with N‐phenyl maleimide
Authors: Bharel Renu , Choudhary Veena , Varma I. K. 
Published: April 2003

AbstractStructural modification of PMMA was done by copolymerizing it with low mole fraction (≤ 0.1) of N‐phenyl maleimide (NPM) using benzoyl peroxide as an initiator. Four copolymers were prepared by changing the mole fraction of NPM in the monomer feed from 0.025 to 0.1. The copolymer composition was determined by 1H‐NMR. An increase in NPM content resulted in an increase in Tg of copolymers. Tensile stress and % elongation decreased, whereas modulus increased with an increase in NPM content. The Flexural strength was not affected by the NPM content. The dynamic mechanical properties were also evaluated in the temperature range of–20 to 100°C. © 1993 John Wiley & Sons, Inc.
Self‐crosslinkable plastic‐rubber blend system based on poly (vinyl chloride) and acrylonitrile‐co‐butadiene rubber
Authors: Manoj N. R. , De P. P. , De S. K. 
Published: April 2003

AbstractThat the melt‐mixed blend of poly (vinyl chloride) and acrylonitrile‐co‐butadiene rubber becomes crosslinked during high‐temperature molding is evident from Monsanto rheometric, solvent swelling, and infrared spectroscopic studies. Dynamic mechanical analysis shows that such a self‐crosslinkable plastic‐rubber blend is miscible in different blend ratios. The degree of crosslinking depends on the blend ratios and the molding conditions. The cross‐linking reaction involves the allylic chlorine sites in poly (vinyl chloride) and the CN group in the nitrile rubber. © 1993 John Wiley & Sons, Inc.
Transport properties of poly(vinyl alcohol) membranes of different degrees of crystallinity. I. Pervaporation results
Authors: Gref R. , Nguyen Q. T. , Schaetzel P. , Néel J. 
Published: April 2003

AbstractDense poly (vinyl alcohol) (PVA) membranes of different crystallinities were prepared and studied in pervaporation of water‐ethanol mixtures. High selectivities to water were obtained with all types of membranes. Permeation fluxes increase exponentially with the water content in the liquid mixture. At a given water content, the membrane permeability decreases drastically when its crystallinity increases. When the pervaporation temperature increases, the permeation flux increases according to the Arrheniuslike law, with a permeation acti‐vation energy that depends strongly on the crystallinity of the membrane. A permeation model, in which the volume fraction of amorphous polymer intervenes in both the sorption and the diffusion laws, was proposed and validated by the experimental data. With the obtained values of the parameters, the permeation Olux can be calculated for membranes of a given crystallinity at any temperature and composition of the water‐alcohol mixture. © 1993 John Wiley & Sons, Inc.
Kinetics of anhydride curing of isophthalic diglycidyl ester using differential scanning calorimetry
Authors: Khanna Umang , Chanda Manas 
Published: April 2003

AbstractThe cure reaction of a model diglycidyl ester, bis‐(2,3‐epoxypropyl)‐1,3‐benzenedicarbox‐ylate, with hexahydrophthalic anhydride as the curing agent and benzyldimethylamine as the catalyst, was studied by differential scanning calorimetry using an isothermal approach over the temperature range 100–135°C. The results indicate that the cure reaction is au‐tocatalytic in nature and does not follow simple nth‐order kinetics. A semiempirical equation for autocatalytic systems containing two rate constants and two reaction orders, viz., 0.5 and 1.5, provided a good phenomenological description of the cure kinetics up to the point of vitrification. With the inclusion of a diffusion factor into this model, it was, however, possible to predict with precision the cure kinetics over the whole range of conversion covering both pre‐and postvitrification stages and over the entire temperature range of 100–135°C employed for isothermal curing. © 1993 John Wiley & Sons, Inc.
Cyclic voltammetry and conductivity investigations of polyaniline
Authors: Bhadani Suraj N. , Gupta Manoj K. , Gupta Sumanta K. Sen 
Published: April 2003

AbstractThe cyclic voltammograms of polyaniline prepared electrochemically were examined in the range −0.2 to 1.0 V vs. SCE in the presence and absence of aniline in the acqueous solution of HBF4. Cyclic voltammetry studies show that the polymeric film suffers degradation when the potential exceeds +0.85 V, and below this potential, it is quite stable. The redox reaction of the film is reversible. The polymeric film synthesized at low temperature and high acid concentration exhibits higher electronic conductivities. © 1993 John Wiley & Sons, Inc.
Correlation of binder mechanical properties with functionality type and molecular weight distribution for hydroxy‐terminated polybutadienes: 13C‐NMR and SEC studies
Authors: Ramarao M. , Scarish K. J. , Ravindran P. V. , Chandrasekharan G. , Alwan S. , Sastri K. S. 
Published: April 2003

AbstractHydroxy‐terminated polybutadiene (HTPB) liquid prepolymers (I‐IX), with closely similar OH values, M̄n, viscosity, and microstructure, were synthesized by H2O2‐initiated free‐radical polymerization of butadiene in an isopropanol–water solvent system. However, binders obtained by curing HTPB polymers showed wide variations in their sol content, cross‐link density, and mechanical properties. These variations were atributed to the differences in functionality‐type distribution (FTD) and molecular weight distribution (MWD) of the polymers. FTD was interpreted in terms of ‐type primary hydroxyls. [V/G] showed excellent linear correlation with the elongation at break (E) of the binders. The polymers exhibited bimodal MWD and this behavior was discussed in relation to two different initiation processes occurring. The high molecular weight fraction (Fh) of the various polymers was determined by reverse‐phase HPLC and showed good correlation with E. The sol content and cross‐link density of the binders also showed good correlation with the parameter V/GFh. The parameters [V/G] and Fh provide acceptance criteria for blending different batches of polymers for propellant formulations. © 1993 John Wiley & Sons, Inc.
Electrostatic and steric stabilization of PVC primary particles
Authors: Kiparissides C. , Moustakis I. , Hamielec A. 
Published: April 2003

AbstractProblems related to the formation and stability of primary particles in VCM suspension and bulk polymerization were theoretically analyzed, based on the DLVO (Deryaguin‐Landau‐Verway‐Overbeek) and HVO (Hesselink‐Vrij‐Overbeek) theories of stability of colloidal systems. In the absence of secondary stabilizers, PVC primary particles were solely stabilized by negative electric charges, as a result of the presence of HCl formed by a chain transfer reaction of chloride redicals to PVC polymer chains. The dependence of the stability of primary particles on the ionic strength of the medium, temperature, and total particle charge was quantitatively investigated in terms of the stability ratio and the particle coalescence rate constant. The steric stabilization of primary particles, arising from the addition of surfactants or polymers to the monomer phase, was examined, using the HVO theory. It was shown that PMMA improved the stability of primary particles and, thus, could alter the particle agglomeration kinetics. The effects of molar mass and the amount of the absorbed PMMA, as well as the influence of solvent quality on the steric stabilization of primary particles, were also investigated. The experimental results, published on the electrostatic and steric stabilization of PVC primary particles, were in good agreement with the theoretical predictions obtained in this study. © 1993 John Wiley & Sons, Inc.
Formation of polymeric foams from aqueous foams stabilized using a polymerizable surfactant
Authors: Raj W. R. Palani , Sasthav Mohan , Cheung H. Michael 
Published: April 2003

AbstractPolymerization of foams formed by purging with nitrogen an aqueous precursor system made up of a polymerizable surfactant, a monomer, and a cross‐linking agent yielded stable polymeric foams. The precursor system for foaming contained hydrophobic components (methyl methacrylate as monomer and ethylene glycol dimethacrylate as cross‐linking agent) in water and was stabilized using the polymerizable surfactant potassium acrylamidostearate. The phase‐behavior study for the precursor system was conducted followed by an investigation of the stability of the foams obtained on purging with nitrogen. Sonicating the precursor systems during the process of purging with nitrogen gas followed by polymerization resulted in aqueous foams having a uniform cell size. The aqueous foams were polymerized by a free‐radical mechanism using photoinitiated and thermal techniques to form stable polymeric foams. The morphology and density of the polymeric foams obtained was determined and observed to be significantly dependent on the composition of the aqueous precursor that was foamed. These results indicate the feasibility of synthesizing polymeric foams without using hydrocarbon solvents or blowing agents during polymerization. © 1993 John Wiley & Sons, Inc.
Polyesters containing sulfur. II. Products of reaction of polyesters with elemental sulfur
Authors: Kultys Anna , Podkościelny Wawrzyniec 
Published: April 2003

AbstractNew polyester–sulfur compositions with increased tensile strength were obtained by heating polyesters derived from diphenylmethane‐4,4′‐di(methylthioacetic acid) and ethylene or diethylene glycol with elemental sulfur. The hardness, tensile, thermomechanical, as well as some electrical properties of reaction products were determined. © 1993 John Wiley & Sons, Inc.