bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal and mechanical properties of aryl ketone polymers and their composites
Authors: Barton J. M. , Lloyd J. R. , Goodwin A. A. , Hay J. N. 
Published: April 2007

AbstractCarbon fibre composites of polyaryletheretherketone (PEEK), APC‐2, have been extracted with mixed solvents in order to separate the polymer matrix. A comparison of the crystallisation behaviour of this material with standard PEEK has been made. Nucleation by carbon fibre was only observed after the samples were sheared and this was attributed to stress‐induced nucleation. On allowing to relax in the melt, and in the absence of residual stresses, no surface nucleation by the carbon fibres was observed.The fracture toughness and flexural modulus of the composite are discussed in terms of thermal history, as well as the dynamic mechanical thermal behaviour.
Thermal behaviour and morphology of copolyterephthalates derived from trimethylene glycols
Authors: González César C. , Bello Antonio , Pereña José M. , Pérez Ernesto 
Published: April 2007

AbstractThe thermal behaviour and the morphology of four polyterephthalate samples have been studied. Two of these samples are the pure homopolymers poly(trimethylene terephthalate) (PTMT) and poly(oxyditrimethylene terephthalate) (PTMTMT), while the other two are copolymers of both polyesters with 13 and 33% by weight of PTMTMT. It was found that the insertion of units of PTMTMT in the copolymers derived from PTMT produces a depression of the glass transition and melting temperatures as a consequence of the higher flexibility of the former units, and several equations have been tested to fit that depression. Moreover, the crystallization rate of PTMTMT was found to be very slow, and the need for higher supercoolings to crystallize the samples in a reasonable time, as the PTMTMT content increases, implies the formation of a greater number of nuclei, with subsequent inconvenience when trying to follow the evolution of the radii of the observed spherulites. On the other hand, well developed spherulites were obtained for the samples rich in PTMT, and two different kinds of this superstructure were observed, depending on the crystallization temperature.
Influence of resin structure on the addition of ethanol to isobutene in the vapour phase
Authors: Iborra Montserrat , Tejero Javier , Izquierdo José F. , Cunill Fidel 
Published: April 2007

AbstractThe addition of ethanol to isobutene in the vapour phase has been studied on four commercial macroporous resins. The acid group content of the resins used was about 5 meq g−1, and their degrees of crosslinking were 12, 16, 18 and 20%. Differential conversions were measured for ethanol‐isobutene‐nitrogen feeds at 53–78.5°C and atmospheric pressure, far from limitation by chemical equilibrium. The rate data showed that isobutene has an enhancing effect on the reaction, whereas ethanol has a strong inhibitory effect in the range studied. The four catalysts showed similar behaviour. At the lower temperatures explored all the resins have similar catalytic activity, but at the highest temperature the resin with 18% divinylbenzene showed the highest activity. This maximum activity can be explained by a greater accessibility to the acid groups, which is in agreement with the literature.
Spin‐labelling studies of the conformation of poly(vinyl alcohol) derivatives
Authors: Tenhu Heikki , Sundholm Franciska 
Published: April 2007

AbstractPoly(vinyl acetate‐co‐vinyl alcohol‐co‐vinyl cinnamate) containing 12% residual acetate groups and 2% cinnamate groups has been studied in aqueous solution with a spin‐label covalently bound in the polymer chain. The polymer undergoes a conformational change around room temperature. In addition, it is suggested that the change in conformation is followed by a change in the aggregation state of the polymer molecules.
DSC study of the interaction of 2‐mercaptobenzothiazole, sulphur, ZnO and stearic acid in the absence of rubber
Authors: Luyt Adriaan S. , McGill William J. , Shillington David 
Published: April 2007

AbstractThe interactions between mixtures of 2‐mercaptobenzothiazole (MBT), sulphur, ZnO and stearic acid were studied by DSC in the absence of rubber. MBT was thermally stable up to its melting point of 174°C, but molten MBT reacted with ZnO as well as with molten zinc stearate, to form zinc mercaptobenzothiazole (ZMBT). The reactions did not go to completion, presumably as further reaction was hindered by solid ZMBT which was thermally stable up to its melting point of 330°C. MBT dissolved in molten sulphur and no thermal events that could be attributed to MBT/sulphur interaction were detected. A mixture of MBT/sulphur/ZnO heated to 190°C yielded ZMBT, together with residual MBT and sulphur (residual ZnO was not measured). In a mixture of MBT/ZnO/stearic acid, the formation of zinc stearate occurred at a lower temperature than in the absence of MBT and preceded the formation of ZMBT.
Synthesis of polypyrrole having an alkyl side chain
Authors: Kaeriyama Kyoji , Masuda Hideyuki 
Published: April 2007

AbstractElectrochemical polymerisation of 3‐octylpyrrole (OCPY) was studied. Its conductivity was 5 S/cm at an optimal current density of 0.5 mA/cm2. Cyclic voltammograms of poly(3‐octylpyrrole) (POCPY) films were measured in the presence of various electrolytes and their shapes were virtually independent of the electrolytes used. There was an anodic peak at 0.16 V (versus Ag) and a cathodic peak at 0.12 V. Optical absorption spectra were measured at various levels of doping. The neutral film showed one peak at 3.5 eV, corresponding to the π‐π* transition. The oxidised film showed two peaks in the lower energy regions, suggesting it was in the bipolaron state. Scanning electron microscope (SEM) observation revealed a process of unique morphology formation.
Step‐growth polymerization of aniline with unsaturated aldehydes
Authors: Šebenik A. , Osredkar U. , Zidar R. 
Published: April 2007

AbstractAbstract: Reactions between aniline and acrolein, crotonaldehyde or cinnamaldehyde were studied by ID and 2D ' H and 13C NMR spectroscopy and by GPC. In the first step, two main reactions cursimultaneously: the addition of the amino groups of aniline to the double bond and to the aldehyde group of the unsaturated
aldehydes. In thc ncxt step of the reaction high molecular weight, red coloured resins soluble in organic solvents are formed. The molecular weights of the resins depend on reaction conditions and on the type of unsaturated aldehyde. From the concentration dependence of different molecular weight products on reaction time the rateconstants werecalculated. It was found that the values for the rate constants depend on the type and quantity of catalyst, on the reaction media and on the type of aldehyde.
Polyaniline/polyurethane. LiCIO4 conducting polymer composite
Authors: Yi‐Rui Chen , Dong‐Pu Fang , Xin‐Hua Xu 
Published: April 2007

AbstractIn the present paper, we describe a novel electrically conducting composite, PAn/Pu. LiClO4. The composite was obtained by in‐situ polymerization of aniline on to Pu. LiClO4 film. The composite film doped with HCl showed a conductivity of c. 1.65 S/cm, with good stability in air and good mechanical strength. The composite increased the interface area 2 to 8 times and depressed the contact resistance between the two polymer phases. A battery was constructed from this composite. The coulombic efficiency was c. 96%.
Influence of synthesis on the structure of electrochemically prepared electrically conducting polymers
Authors: Mitchell G. R. , Davis F. J. , Kiani M. S. 
Published: April 2007

AbstractThe inherent possibility of structural anisotropy in polypyrrole and other heterocyclic systems is introduced. By selecting the appropriate electrochemical variables including monomer and dopant type this intrinsic molecular anisotropy may be used to prepare films with well defined global anisotropy, in which the planes of the pyrrole rings prefer to lie parallel to the electrode surface. The conditions for obtaining such materials are discussed and some of the effects of these novel anisotropic structures on the resultant properties are highlighted. Attention is directed at charge transport and optical properties.
Doping studies of heterogeneous langmuir—blodgett thin films containing poly(3‐hexyl thiophene)
Authors: Watanabe Itsuo , Rubner Michael F. 
Published: April 2007

AbstractLangmuir‐Blodgett multilayer thin films fabricated from mixed monolayers containing poly(3‐hexyl thiophene) and stearic acid were rendered electrically conductive with strong oxidizing agents such as SbCl5, I2 and NOPF6. In‐situ doping studies using dopants introduced in the gas phase revealed that the increase in conductivity was due to the formation of bipolaron‐type charged defect sites on the polymer backbone. The highest level of conductivity was achieved by doping with NOPF6 from solution (about 3 S/cm). Solution phase doping, however, was found to disrupt the molecular organization of the multilayer film completely. In contrast, doping could be accomplished with retention or modification of the original molecular organization if carried out in the gas phase using either SbCl5 or I2. The resultant in‐plane conductivities were a few orders of magnitude lower than films doped from solution due to the heterogeneous nature of the doped multilayer film. The conductivity of multilayer films doped with SbCl5 was found to be stable in vacuum whereas the conductivity of films doped with I2 decayed rapidly in either vacuum or air.
Doped glassy carbon materials (DGC): Their synthesis from polymeric precursors and investigation of their properties
Authors: Neenan Thomas X. , Callstrom Matthew R. , Bachman Bonnie J. , McCreery Richard L. , Alsmeyer Daniel C. 
Published: April 2007

AbstractA low temperature route (200–600°C) to the preparation of glassy carbon containing high levels of heteroatoms has been developed. The synthesis involves the preparation of diacetylenic oligomeric precursors, molding of these materials, and thermal treatment under controlled conditions to form glassy carbon. Materials have been prepared which contain high levels (10–15%) of nitrogen, fluorine, and silicon by covalent attachment of these heteroatoms to the diacetylene oligomers. A Raman study confirmed the presence of diagnostic peaks for glassy carbon, including the E12 fundamental at 1582cm−1 and the A1g at 1360 cm−1. The physical properties of these materials, including thermal stability, microscopic structure, density, and elastic modulus are reported.
A study of the relationship between setting chemistry and properties of modified glass‐poly(alkenoate) cements
Authors: Wasson Eleanor A. , Nicholson John W. 
Published: April 2007

AbstractA study aimed at increasing the understanding of the setting chemistry and final structure of glass‐poly(alkenoate) [‘Glass‐Ionomer’] cements has been carried out in which the decomposition of glasses in aqueous solutions of an organic acid has been examined. Two glasses, an aluminosilicate and a fluoroaluminosilicate respectively, were washed with solutions of acetic acid and the washings analysed by ICP‐OES. For both glasses calcium and aluminium were found to be released under all conditions of acid‐washing. In addition, significant quantities of silicon and sodium were also found to be released. These findings have led to a reappraisal of both the precise mode of setting and the final structure of these materials. The pattern of ion release was also capable of providing some information on the structure of the phases present in the original glass.
Bioconversions of cellulose—A major source of material for the biochemical industry
Authors: Kennedy John F. , Melo Eduardo H. M. 
Published: April 2007

AbstractThe abundance and renewability of lignocellulosic materials renders them to be a promising feedstock for production of energy, food and chemicals. Enzymatic hydrolysis of lignocellulose into fermentable sugars has been extensively studied in order to reach a more efficient utilization of renewable biomass energy. Enzymatic hydrolysis of lignocellulose means degradation of cellulose to D‐glucose, but the mechanism of cellulose hydrolysis by enzymes is still not well understood.This paper deals with processes for obtaining lignocellulosic materials, for converting them into fermentables by use of acid and enzyme hydrolysis, and for fermentation of the sugars to useful products.
Photoresponsive polymers IV. Conformational changes of polypeptides upon irradiation
Authors: Hallensleben Manfred L. , Menzel Henning 
Published: April 2007

AbstractPoly(5‐(4‐phenylazobenzyl)‐L‐glutamate) was synthesized to study the photoinduced helix coil transition of a unipolymer. The crucial point in the synthesis is the selective esterification of the L‐glutamic acid, which was carried out as an alcoholysis of the N‐protected cyclic anhydride. The 5‐ester was treated with phosgene to óbtain the N‐carboxyanhydride, which was polymerized by base catalysis. The polymer was investigated in dilute dioxane solutions. The photoinduced transition was followed by means of UV spectroscopy for the chromophore and viscosimetric experiments for the configuration of the polymer chain. The changes in viscosity are more complex than expected for a helix coil transition, so aggregates have to be taken into account.
Synthesis, characterization and degradation of aliphatic polyanhydrides
Authors: Albertsson A.‐C. , Lundmark Stefan 
Published: April 2007

AbstractPoly(adipic anhydride) (PAA), poly(sebacic anhydride) (PSA) and poly(dodecanoic anhydride) (PDA) were prepared from the mixed anhydrides of diacids and ketene (in tetrahydrofuran (THF) solution), the mixed anhydrides being subjected to melt polycondensation. The polymerizations were carried out in the presence of diethyl zinc as a catalyst. The polymers were characterized by means of 1H NMR, IR spectroscopy, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The polymer yields and the molecular weights of the polymers increased in the presence of catalyst. From these results a mechanism for the reaction is proposed. The highest melting temperature of the resultant polymers was obtained from PDA (Tpeak = 90°C). The heat of fusion was approximately 100 J/g (PDA). The number‐average and weight‐average molecular weights of the polyanhydrides were 18000 and 33000 respectively (PDA). Poly(anhydride)‐b‐poly(ethylene glycol) and poly(anhydride)‐b‐poly(tetramethylene glycol) copolymers were prepared from the mixed anhydrides of dodecanoic acid, poly(ethylene glycol)‐succinic half‐ester and poly(tetramethylene glycol)‐succinic half‐ester respectively. The block copolymers were characterized by means of 1H NMR, IR and GPC. The hydrolytic degradation of PDA has been studied in a buffered salt solution (pH 7·2) at 37°C by examining the changes in molecular weight, heat of fusion, mass loss and surface structure of melt‐pressed PDA strips.
Poly(alkylene phosphates): Bioanalogous synthetic polymers
Authors: Penczek Stanislaw , Baran Jolanta , Biela Tadeusz , Lapienis Grzegorz , Nyk Andrzej , Klosinski Pawel , Pretula Barbara 
Published: April 2007

AbstractPreparation, some properties and applications of the bioanalogous poly(alkylene phosphates), obtained according to the methods elaborated in these authors' laboratory, are reviewed. Ring‐opening polymerization, polyaddition, and two‐step polycondensation methods are effective in the synthesis of polymers with various moieties of nucleic and teichoic acids (NA and TA, respectively). The major aim of the work is to find relatively simple methods allowing high molecular weight polymers to be prepared. Thus, preparation of poly(glycerol phosphate) and poly(trimethylene phosphate) bearing NA bases and related polymers with M¯n ⩾ 104 are described.
Design of poly(α‐malic acid)‐5FU conjugate exhibiting antitumor activity
Authors: Ouchi Tatsuro , Kobayashi Hironao , Banba Toshio 
Published: April 2007

AbstractSince poly(α‐malic acid) is a biodegradable and bioabsorbable lactic acid type polyester having pendent carboxylic acid groups, it is of interest for application as the polymer carrier to covalently attach both a parent drug and a targeting agent. In order to provide a macromolecular prodrug of 5‐fluorouracil (5FU) with reduced side‐effects and exhibiting high antitumor activity, the covalent attachment of 5FU to poly(α‐malic acid) through hydrophobic spacer groups, ester or amide and carbamoyl groups was carried out. In order to estimate the release behavior of 5FU from poly(α‐malic acid)‐5FU conjugates, the hydrolysis of the pendent ester or amide and carbamoyl groups in the conjugates obtained was investigated in vitro using various kinds of aqueous solution at 37°C. The effect on prolongation of life was tested in vivo against p‐388 lymphocytic leukemia in female CDF1 mice by intraperitoneal (i.p.) i.p. injection. These poly(α‐malic acid) 5FU conjugates gave a high survival rate and did not display acute toxicity in the high dose range of 200–800 mg/kg.
Enzyme immobilization in polymer coated liposomes
Authors: Őzden M. Yasar , Hasirci Vasif N. 
Published: April 2007

AbstractIn this study liposomes composed of only dicetylphosphate (DCP), or of a 7:2: 1 (mole ratio) mixture of phosphatidylcholine (PC), dicetylphosphate (DCP) and cholesterol (Chol.( were prepared. Resultant liposomes were coated with varying amounts of poly(1,4‐pyridinium diethylene salt(, P1,4 VN. The polymer was shown to be different from poly(4‐vinylpyridine(, P4VN, which is also obtained from the same monomer. The increase in the coating extent (or thickness( was shown by IR and UV through the increase in the peaks due to polymer. The strength of binding was indirectly shown by being able to obtain scanning electron micrographs for the coated liposomes while it was not possible for the uncoated ones. It was shown that the lipid membrane under the polymeric coat can be removed. The resultant structure is highly permeable in comparison to the impermeable, lipid‐containing form. The activity of the enzyme glucose oxidase was demonstrated using the enzyme encapsulated in the polymeric net.
Synthesis and properties of biodegradable aliphatic polyesters
Authors: Dahlmann Jürgen , Rafler Gerald , Fechner Klaus , Mehlis Burkhard 
Published: April 2007

AbstractThe ring‐opening polymerization of D, L‐dilactide and an equimolar dilactide‐diglycolide mixture has been investigated. Conversion and molecular weight in the lactide bulk polymerization are determined not only by the kinetics of the primary ring‐opening reaction, but also by the concentration and extent of consecutive reactions of reactive groups in the polyester formed. High conversions and high molecular weights are obtained only by high polymerization rates. For the characterization of the polymers, viscosity‐molecular weight relationships for monomer‐containing ‘equilibrium’ polymers and reprecipitated polymers were determined. The application of these polymers in parenteral drug delivery systems for a gonadotropin‐releasing hormone agonist has been investigated.
Controlled‐release model systems
Authors: Połowiński Stefan , Szosland Lidia , Szumilewicz Joanna , Połowińska Alina , Pierzchlewska Aurelia 
Published: April 2007

AbstractThe kinetics of the controlled release of biocides from simple model systems have been studied. Crosslinked dextran, modified crosslinked dextran and ion‐exchange resin (Wofatit) were used as carriers. Salicylic acid, 2,4,5‐trichlorophenol, 8‐hydroxyquinoline and codeine were used as biocides. Some systems were coated with poly(vinyl acetate), acetylchitin or a copolymer of methyl methacrylate with dimethylaminoethyl methacrylate. An exponential equation was proposed for the description of the release kinetics and checked experimentally. Good correlation with the equation was found.
Synthesis, structure and antiviral activity of sulfates of curdlan and its branched derivatives
Authors: Yamamoto Iwao , Takayama Kesayo , Gonda Takashi , Matsuzaki Kei , Hatanaka Ken‐Ichi , Yoshida Takashi , Uryu Toshiyuki , Yoshida Osamu , Nakashima Hideki , Yamamoto Naoki , Kaneko Yutaro , Mimura Tohru 
Published: April 2007

AbstractCurdlan and its branched derivatives having oligo‐L‐ or oligo‐D‐arabinofuranose side chains, D‐glucopyranose side chains or D‐galactopyranose side chains were sulfated with piperidine N‐sulfonic acid or SO3‐dimethylform‐amide complex. The structures of the sulfated polysaccharides were analyzed by elemental analysis and 13C NMR spectroscopy. The 13C NMR spectra of curdlan sulfates were assigned and the degree of substitution (DS) value of each hydroxyl group was obtained. The reactivity was in the order C‐6  C‐4 = C‐2. However, a little different distribution of substituents was observed between curdlan sulfates synthesized with piperidine N‐sulfonic acid and SO3‐DMF complex. Sulfated polysaccharides with high d.s. values showed high anti‐HIV (AIDS virus) activity.
Soluble functional polymers for human haemoglobin modification for blood substitution
Authors: Prouchayret Florence , Bonneaux François , Léonard Michèle , Sacco Daniel , Dellacherie Edith 
Published: April 2007

AbstractAqueous solutions of certain polymers have been used as plasma expanders for a long time. However, these polymer solutions are only capable of correcting the volume of circulation in vivo and in particular they cannot replace the oxygen‐carrying function of blood. This property can be conferred to these polymer solutions by linking human haemoglobin, the natural oxygen carrier, to the polymers in such a way that the oxygen‐binding properties of the free protein are similar to those of blood. Such results can be achieved by designing and preparing special polyanionic derivatives of dextran and polyoxyethylene and linking them to free human haemoglobin under its deoxy form or its oxy form. The resulting covalent conjugates exhibit general properties quite fitted to a use in blood substitution.
Thermoplastic hydrogels
Authors: Brook M. Gordon 
Published: April 2007

AbstractA range of thermoplastic hydrogels which combine the properties of conventional crosslinked hydrogels with the processing convenience of thermoplastics has been developed. The materials can be melt‐processed or cast from solution in organic solvents, making it practical to use them in a wide range of products and to easily combine other materials with them. These hydrogels are noncrosslinked copolymers of hydrophobic and hydrophilic monomers, the intramolecular interactions between the hydrophobic units performing the role of the crosslinks in conventional hydrogels.
Microcrystalline chitosan—Some areas of application
Authors: Struszczyk Henryk , Kivekäs Olli 
Published: April 2007

AbstractMicrocrystalline chitosan existing as a new microcrystalline form of standard poly(2‐deoxy‐2‐amino‐D‐glucose) is a special functional polymeric material suitable for several applications. New areas of microcrystalline chitosan use in the textile industry, waste water treatment and medicine are presented. Microcrystalline chitosan in the applications discussed has practical and economic advantages over standard chitosan.
Polyurethanes as biomedical materials
Authors: Kutay Sezer , Tincer Teoman , Hasirci Nesrin 
Published: April 2007

AbstractPolyurethane films were prepared using diphenylmethanediisocyanate [MDI] or hexamethylenediisocyanate [HDI] and poly(propylene‐ethylene) glycol, in order to test them as biomedical materials specifically for use as skin grafts. Other ingredients such as catalysts, chain extenders, solvents, etc., where not used in order to obtain medical purity.Mechanical properties, oxygen permeation and blood compatibility of these films were examined. Tensile strength, ultimate elongation and elastic modulus values were calculated. An increase in ultimate elongation and a decrease in tensile strength were observed when the amount of isocyanate‐containing compound was decreased in the prepared polymers. Oxygen permeability values also increased with an increase in polyol content of the prepared films. Blood compatibility tests showed that the film surfaces do not have thrombogenicity and can be considered biocompatible.