bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of the molecular weight of ionenes on the cobaltphthalocyanine‐catalysed autoxidation of mercaptoethanol
Authors: Schipper Eugène T. W. M. , Roelofs Alexander H. C. , Piet Pieter , German Anton L. 
Published: April 2003

AbstractIn order to study the promoting effect of polycations on the cobalt(II)phthalocyanine‐tetrasodiumsulphonate (CoPc(NaSO3)4)‐catalysed autoxidation of thiols, it is imperative to know the molecular weight dependence of the polymer. Monodisperse oligomers can often supply a lot of information. To elecidate the mechanism of the promoting effect of 2,4‐ionene, a poly(quaternary ammonium)salt, on the CoPc(NaSO3)4‐catalysed autoxidation of 2‐mercaptoethanol, a series of monodisperse 2,4‐ionene oligomers were prepared. Trimeric 2,4‐ionenes, containing two quaternary ammonium groups separated by four methylene groups, showed a high co‐catalytic activity, and active Co‐aggregates were detected with visible light spectroscopy. The spectroscopic behaviour was in close agreement with that of high molecular 2,4‐ionene/CoPc(NaSO3)4 complexes. In order to achieve this aggregation several oligomeric ionenes have to act concertedly. If the distance between the ionic sites is short the trimer acts as a simple salt in stablizing the aggregates. With respect to the catalytic activity the optimum polycation/catalyst ratio, expressed as the N+/Co ratio, decreased with increasing chain lenght and reached a constant level of 50 at a 2,4‐ionene nonamer. For the trimers and pentamers this ratio is affected by the type of end‐group. All synthesized 2,4‐ionene oligomers exhibited excellent co‐catalytic properties at the optimum N+/Co ratio, with maximum turnover frequencies of 4600 mol thiol/(mol Co s), i.e. 50 times higher than those obtained for the polymer‐free system. In the case of monodisperse 2,4‐ionene pentamer with bromo end‐groups, double Michaelis–Menten kinetics were observed, as also was exhibited by high molecular weight ionene.
Modelling studies of the controlled anionic copolymerization of butadiene and styrene
Authors: Chang C. C. , Halasa A. F. , Miller J. W. , Hsu W. L. 
Published: April 2003

AbstractThe anionic polymerization of isoprene with n‐butyl lithium and polar modifier such as TMEDA and tripiperdinophosphine oxide were studied and kinetic and reactor models are proposed for these systems. Reactor conversion, molecular weight distribution and polymer glass transition temperature had been calculated from the model and compared favorably to the actual data for various combinations of reactor systems and operating conditions. Simulations of the model can be used to design reactor systems and predict polymer properties of large‐scale operations from results of small scale batch reactor runs.
Synthesis of stereoblock poly(methyl methacrylate) via transformation of isotactic‐specific living polymer anion to syndiotactic‐specific anion
Authors: Kitayama Tatsuki , Fujimoto Nobutaka , Yanagida Takatsune , Hatada Koichi 
Published: April 2003

AbstractPolymerization of methyl methacrylate (MMA) by isotactic poly(methyl methacrylate) (PMMA) living anion, prepared with t‐C4H9MgBr in toluene at −60°C, was carried out at −78°C in the presence of trialkylaluminiums (R3Al; R = CH3, C2H5, and n‐C4H9) to obtain a stereoblock PMMA, isotactic PMMA‐block‐syndiotactic PMMA. Among the R3Als, (CH3)3Al gave most effectively the steroblock PMMA with narrow molecular weight distribution. The fraction of rr triad in the syndiotactic PMMA block increased with increase in the ratio of Al/Mg and reached about 76% at a ratio of Al/Mg ≥ 6. The method was also used to prepare stereoblock copolymer comprising isotactic PMMA block and syndiotactic block of butyl methacrylate. Stereocomplex formation and solution viscosity of the stereoblock PMMA were also studied.
Dipole moments of styrene/4‐vinylpyridine copolymers—II: Relation to microstructure
Authors: Yilmaz Elvan , Küçükyavuz Zühal 
Published: April 2003

AbstractMean‐square dipole moment values of styrene/4‐vinylpyridine (S4VP) copolymers determined at 25–60°C in 1,4‐dioxane solutions were related to the microstructure of the chains. Data on the synthesis and dipole moments of S4VP copolymers were used to calculate the distribution of triad fractions and effective dipole moments of styrene, S‐centred, and 4‐vinylpyridine, V‐centred, fractions in the copolymer chains. The relative magnitudes of the effective dipole moment values calculated for each type of triad reflect the effect of dipole–dipole interactions on these values.
Performance of polysulfone/carboxylated polysulfone membranes
Authors: Lau Wayne W. Y. , Jiang Youqing 
Published: April 2003

AbstractMembranes were made from miscible blends of polysulfone (PSf) and carboxylated polysulfone (CPSf) having an average of 0.45 and 0.87 COOH groups per repeated unit. Membranes made from PSf and CPSf alone showed low separation for NaCl, glucose, polyethylene glycol (PEG) of various molecular weights and bovine albumin, from aqueous solutions under an applied pressure of 50 psig and higher. Membranes made from PSf/CPSf of varied blend composition showed higher separation factors for the above solutes. Highest separation was observed in membranes made from an 80/20 wt% PSf/CPSf 0.45 blend, which yielded a separation factor of 0.60 for NaCl, 0.97 for glucose, 0.98 for PEG and 0.99 for bovine albumin under an applied pressure in the range 50–150 psig. This higher performance is believed to be a result of a synergism between PSf and CPSf 0.45 to give a membrane morphology unique among the PSf/CPSf membranes.
The study of complex mineral silicates by trimethylsilylation
Authors: ap Kendrick Dafydd , Montecinos Marcia , Parsonage John R. 
Published: April 2003

AbstractThe Lentz trimethylsilylation technique has been applied to study four micas: biotite, phlogopite, muscovite and suzorite. The Lentz derivitisation technique is shown to be independent of the exact amount of phase transfer agent (propan‐2‐ol or ethanol) present in the trimethylsilylation of the micas as long as the ratio of mineral to hexamethyldisiloxane is held constant. The polyorganosiloxane product distribution is shown to be largely dependent on the amount and distribution of Al3+ present in the tetrahedral layers of the micas.
Acoustical studies on polyvinylchloride in dimethylformamide
Authors: Sundaresan B. , Srinivasarao A. 
Published: April 2003

AbstractUltrasonic velocity studies were undertaken on solutions of polyvinylchloride (PVC) in dimethylformamide (DMF) in the concentration range 0–3% by weight, at an RF frequency of 2 MHz at three different temperatures, 303 K, 313 K and 323 K. The observed non‐linear increase in ultrasonic velocity with increase of PVC concentration is attributed to the segment–segment interaction which causes molecular association between PVC and DMF.
Combined electrochemical and chemical synthesis of thick polypyrrole layers and their characterization
Authors: Omastová Mariá , Lazár Milan , Košina Stanislav 
Published: April 2003

AbstractThe presence of pyridinium chlorochromate as an oxidizing agent in acetonitrile solution containing the monomer and the doping agent significantly accelerates electrochemical polymerization of pyrrole. The thickness of poly pyrrole layers produced by this combined electrochemical and chemical synthesis reaches several milimetres for the 60 min polymerization reaction.The influence of pyridinium chlorochromate concentration on the rate of polymer formation and the amount of released gas was investigated during the combined synthesis of polypyrrole. The polypyrrole prepared was characterized by ESCA analysis.
Properties of carbon fibers modified by oxygen plasma
Authors: Jin Byung Suk , Lee Kwang Hee , Choe Chul Rim 
Published: April 2003

AbstractOxygen plasma treatment was used to introduce functional groups on the surface of polyacrylonitrile‐based carbon fibers. The fiber surface was examined by X‐ray photoelectron spectroscopy after treatment. The amount of functional groups on the fiber surface initially increased with increasing treatment time up to 2 min, thereafter remaining constant. The variation of surface energy with plasma treatment showed a similar trend. The plasma treatment affected the surface area and the mechanical properties of carbon fibers. The surface area increased but the mechanical properties decreased with increasing treatment times. The plasma treatment also changed the morphology of the fiber surface.
pH‐dependent hydrolysis and drug release of chitosan/polyether interpenetrating polymer network hydrogel
Authors: Yao Kang‐de , Peng Tao , Xu Mei‐xuan , Yuan Chen , Goosen Mattheus F. A. , Zhang Qi‐qing , Ren Lei 
Published: April 2003

AbstractThis paper describes a novel hydrogel based on crosslinked chitosan with glutaraldehyde interpenetrating polyether polymer network. The gel can hydrolyse in acid at 37°C due to the cleavage of imine bonds within the network. At pH≥7, there is no hydrolysis. The pH‐dependent release of cimetidine from the gel was also investigated.
Synthesis, characterisation and catalytic activity of styrene–divinylbenzene copolymer (XAD‐2) bound palladium (II) complex
Authors: John Jacob , Ram R. N. 
Published: April 2003

AbstractPolymer‐anchored Pd(II) complex catalyst was sythesised by sequential attachment of 1,2‐diaminopropane as a ligand to the chloromethylated commercially available styrene‐divinylbenzene copolymer (XAD‐2). The catalyst was characterised using techniques such as FTIR, SEM, EPR, and UV‐VIS reflectance spectroscopy. Other physicochemical properties, such as bulk density, moisture content, swelling and surface area by the BET method at low temperature by nitrogen adsorption, were also studied. The catalyst was tested for the rate of hydrogenation of cyclohexene. The influence of various factors such as temperature, concentration of catalyst, substrate, and quantity of solvent have been determined. The results are compared with the homogeneous analogue. The recycling efficiency of the catalyst was also studied.
A comparative study of the thermal discharge behaviour of cellulose diacetate and cellulose triacetate films
Authors: Naidu Y. R. Vidyadhar , Sagar D. S. , Sharma A. K. 
Published: April 2003

AbstractThe thermal discharge behaviour of cellulose diacetate (CA2) (39% acetyl content) and cellulose triacetate (CA3) (44% acetyl content) films was studied at different polarizing temperatures and fields. Cellulose diacetate exhibited two peaks, one at low temperatures and the other at high temperatures, whereas cellulose triacetate exhibited only one peak. The origin of these peaks in CA2 is attributed to dipolar orientation and space charge polarization respectively, while the only peak in CA3 is due to space charge polarization. The difference in thermal discharge behaviour of CA2 and CA3 is attributed to the difference in acetyl contents of the two acetates.
Interpolymer complexes. Properties and characterization
Authors: Leiva A. , Gargallo L. , Radić D. 
Published: April 2003

AbstractInterpolymer complex formation between poly(N‐vinyl‐2‐pyrrolidone) (PVP) and poly(monomethyl itaconate) (PMMel) has been studied. Data from Dynamic Light Scattering show at least two different size distributions of polymer complex (PC). The PC size distributions increase when the temperature increases. Viscosity measurements were also performed in order to estimate the polycomplex segmental density. From these results it can be concluded that PVP and PMMel give rise to a polycomplex formation and the driving force for this association is hydrogen bonding as much as hydrophobic interactions.
Effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile using dialkylmagnesium as catalyst
Authors: Nakano Yasuhiro , Hisatani Kunio , Kamide Kenji 
Published: April 2003

AbstractAn attempt was made to clarify the effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile (AN) initiated by dialkylmagnesium (R2Mg) above 100°C. The triad isotacticity (i.e. the content of mm (m: meso)) as well as the viscosity‐average molecular weight (M̄v) of polyacrylonitrile (PAN) increased when trialkylaluminum (R3Al) and trialkylboron (R3B) were used as additives. Diisobutylaluminum hydride [(i‐C4H9)2AlH] was found to be the best additive. in the stereospecific polymerization of AN, giving PAN with higher (mm) content (0.63), higher M̄v value (5.2 × 104), and a yield approximately double that obtained using (n‐C6H13)2Mg alone. When the (n‐C6H13)2Mg/(i‐C4H9)2AlH system was used, the yield, (mm), and M̄v of PAN increased with polymerization temperature (Tp); maximum values of yield, (mm), and M̄v were obtained at c. 130°C. The optimum amount of additives was approximately equimolar to R2Mg as initiator. The 13C chemical shift of α‐carbon in R2Mg at 90°C shifted by mixing with R3Al and R3B, respectively, indicating the existence of interaction between R2Mg and the additives. The main role of the additives is considered to be suppression of the self‐association of R2Mg by strong interaction with R2Mg.
Dielectric behaviour of cyanoethylated cellulose
Authors: Saad Gamal R. 
Published: April 2003

AbstractThe dielectric characteristics of cyanoethylated cellulose samples having different degrees of substitution have been investigated at different frequencies from 0.1 to 10 KHz and at temperatures from −40°C to 180°C. Two relaxation processes, designated as α and β in order of decreasing temperature, were recognised. The low temperature β‐relaxation is expected to be due to local motion of anhydroglucose rings, while the α‐relaxation is related to the side group motion. The data obtained are discussed in terms of the progressive destruction of the fibre structure, together with the increase of side group polarity due to cyanoethylation.
Surface modification of kaolin. 1. Covalent attachment of polyethylene glycol using a urethane linker
Authors: Molphy Marylou , Laslett Robert L. , Gunatillake Pathiraja A. , Rizzardo Ezio , Mainwaring David E. 
Published: April 2003

AbstractThe kaolin surface was modified through surface reaction in order to tailor the colloidal behaviour of the particles. A molecular weight series of polyethylene glycols was attached to the surface hydroxyls, using a urethane linker, by reaction with toluene 2,4‐diisocyanate. The change in the surface was monitored and the surface products identified using Diffuse Reflectance Infrared Fourier Transform Spectroscoy (DRIFTS) and solid‐state carbon‐13 NMR spectroscopy. The strength of attachment was evaluated by extraction with solvents for urethanes and poly(ethylene oxides). The surface coverage of polymer chains was quantified using a combination of two methods. Potentiometric titration was used to determine the amount of urethane formed on the surface and the number of terminal isocyanate groups available for subsequent reaction with the hydroxy‐terminated polymer. The grafting density of poly(ethylene oxide) on to the kaolin surface was determined through elemental analysis.
The effect of polymers on the crystallisation of n‐alkanes from solution, part 1. Preparation and investigation of spin‐labelled fumarate–vinyl acetate copolymers
Authors: Davidson Iain G. , Cameron G. Gordon 
Published: April 2003

AbstractSpin‐labelled fumarate‐vinyl acetate (FVA) copolymers with octyl (C8) and octadecyl (C18) ester groups were prepared and characterised. An interaction between the C18FVA and the developing crystals of n‐dotriacontane growing from dodecane solution was observed as a slow‐motion component in the electron spin resonace (ESR) spectrum of the system. The C8FVA showed no such behaviour, the spectrum being entirely of the motionally narrowed type through out the crystallisation process. Above the cloud point of the system, no interaction between the polymer and alkane could be detected either in the ESR spectra or from measurements of the rotational correlation times of the spinlabel nitroxide.
Unified approach to living and non‐living cationic polymerization of alkenes
Authors: Matyjaszewski Krzysztof , Sigwalt Pierre 
Published: April 2003

AbstractThe observation of various features of living polymerizations (‘theoretical’ molecular weights, narrow molecular weight distribution) in a large number of carbocationic polyerizations has led to the conclusion that termination and transfer were suppressed in these ‘living’ systems, while they played a predominant role in the ‘classic’ carbocationic polymerizations. This suppression has been attributed to the presence of new types of active sites, such as ‘stretched’ covalent bonds or ‘stabilized’ carbocations.In the present article, a comparison of the data observed with the ‘classic’ and the ‘living’ systems shows that the active sites are similar, with only a change in the relative proportion of carbocationic species, which reduces the rate and favors complete initiation. This means that these ‘living’ systems are generally only apparently living, since termination and transfer reactions also occur and are hidden because the molecular weights of the ‘living’ polymers are typically low. Transfer and termination may, however, be considerably reduced or even suppressed by working at very low temperatures, as is also the case for ‘classic’ systems.
Metal chelates with some cellulose derivatives. Part I. Preparation and characterization of chromium (III)–carboxymethyl cellulose complexes
Authors: El‐Saied Houssni , Basta Altaf H. , Abdel‐Hadi Afkar K. , Hosny Wafaa M. 
Published: April 2003

AbstractA systematic spectrophotometric study on the complexation of chromium (III) ion with sodium carboxymethyl cellulose (CMC) was carried out. The effects of the degree of substitution (DS) of the polymer, the concentrations of Cr(III) and CMC solutions, the pH and temperature on the complex formation were studied in the aqueous state. CMC complexes with Cr(III) were characterized by elemental analysis, magnetic moment and spectral (Vis and IR) data. The results showed that CMC (L) chelated to the metal ion according to the formula CrL2 · 2H2O. The ligand field parameters, namely Dq, B and β were calculated; the β‐values indicate strong covalency in the ligand σ bond. The IR spectra revealed that the chelating sites of CMC are not only the carboxymethyl groups, via the ether‐ and the carboxyl‐oxygen atoms, but also the secondary hydroxyl groups.
Asymmetric induction in forming poly(olefin sulphone)s
Authors: Fawcett Allan H. , Malcolm R. Karl 
Published: April 2003

AbstractPoly(1‐olefin sulphone)s have been prepared from olefins with a chiral centre at the carbon atom adjacent to the double bond. In 13C and 1H NMR studies on the polymers obtained by free radical copolymerisation it has been found that the chirality of a main chain methine carbon that forms part of the backbone depends upon the chirality of the carbon initially present within the same hydrocarbon residue. The introduction of bulky groups into the chiral group of the monomeric olefin increased the ratio of diastereoisomers formed within the residue. In the most favoured case 69% of the backbone chiral centres were fixed with reference to the side chain structures. By employing a simple theory based upon an enumeration of steric interactions and upon the γ‐gauche effect on carbon chemical shifts, it was deduced that the main chain chiral centre preferred to adopt the opposite stereochemistry to that of the side chain when that carries an ethyl group, a methyl group and a hydrogen atom. A bias was also found at the backbone when the monomer chiral centre contained polar acid or ester groups.
The self‐condensation of 4‐bromopyridine
Authors: Feast W. J. , Tsibouklis J. 
Published: April 2003

AbstractThe easily accessible, water soluble, conjugated polymer poly(4‐bromopyridine), has been synthesised by the self‐condensation of 4‐bromopyridine at various temperatures and also in the presence of methyl iodide. The structure of the material is complex with a variety of sub‐units; possible structures are discussed in the light of a detailed spectroscopic analysis.
Radiation assisted compatibilisation of blends of vinylidenefluoride polymers with fluorosilicone elastomers by means of crosslinking coagents
Authors: Mascia L. , Pak S. H. , Caporiccio G. 
Published: April 2003

AbstractAn experimental study was carried out to demonstrate the possibility of compatibilising blends of polyvinylidenefluride with minor amounts of fluorosilicone elastomer, thereby achieving better low temperature ductility without excessively reducing the melting point and degree of crystallinity of the fluoropolymer.The principle that has been explored is the use of multifunctional crosslinking agents acting as a common solvent for the two polymers during mixing, and providing interpenetrating networks through the two polymer phases by means of peroxide‐induced crosslinking reactions.It has been found that mixtures of triallyl isocyanurate with diallyl phthalate are particularly effective in compatibilising the combination of polymers in question, giving the best overall balance of properties. Compatibilisation was enhanced by grafting part of the coagent on to the chains of the fluoropolymer prior to being blended with the fluorosilicone gum. Further evidence for enhanced compatibilisation by such a procedure was obtained from dynamic mechanical tests, which revealed an increase in glass transition temperature for the fluorosilicone phase and a suppression of α‐relaxations in the fluoropolymer component.
Synthesis of polyaniline/polytoluidine block copolymer via the pernigraniline oxidation state
Authors: Mattoso Luiz H. C. , Oliveira Osvaldo N. , Faria Roberto M. , Manohar Sanjeev K. , Epstein Arthur J. , Macdiarmid Alan G. 
Published: April 2003

AbstractPolyaniline was electrochemically synthesized in the emeraldine oxidation state and then converted to the pernigraniline oxidation state by applying an electric potential under optimized conditions. The stability/reactivity of polyaniline in the pernigraniline oxidation state was evaluated in various aqueous media. The products of the reduction of the pernigraniline oxidation state by o‐toluidine were analyzed by gel permeation chromatography, ultraviolet–visible and infrared spectroscopies, and cyclic voltammetry. The results are consistent with the synthesis of a diblock copolymer of polyaniline/poly(o‐toluidine) and also of some poly(o‐toluidine) homopolymer in the emeraldine oxidation state as a side product.
Blood compatibility of poly(ether urethane)–nylon 6 block copolymer
Authors: Seo Seung Won , Ha Wan Shik 
Published: April 2003

AbstractPoly(ether urethane) (PEU)–nylon 6 A–B–A triblock copolymer was synthesised. Correlation of blood compatibility with morphological and surface energetic properties of the block copolymer film was investigated. The block copolymer film exhibited a suppressing effect on thrombus formation and it is suggested that controlling the crystallite size of the nylon 6 block in the block copolymer by regulating the copolymer composition is an important factor in the antithrombogenicity.