bluuebunny/crossref_metadata_2025_split huggingface dataset:
Helix formation of charged polypeptides in polyion complexes with weak and strong polyelectrolytes prepared in aqueous alcohols
Authors: Hirose Tetsuya , Satoh Mitsuru , Komiyama Jiro 
Published: April 2003

AbstractUsing circular dichroism, the helix contents of sodium poly(L‐glutamate) (PLGNa) and poly(L‐lysine) hydrobromide (PLLHBr) in their weak and strong polyelectrolyte complexes have been estimated in aqueous alcohol solutions. Helix (de)stabilization observed in the systems is compared with earlier results on the PLGNa/PLLHBr polyion complex.
Interfacial rheology of uniform polymer dispersions
Authors: Wang S. Q. , Inn Y. W. 
Published: April 2003

AbstractThe effects of high oscillatory shear on the viscosity of a model polymer dispersion of solid particles was investigated. A dispersion of glass beads in poly(dimethyl siloxane) (PDMS) is uniform and free of any agglomeration. When sheared at low stress levels, the dispersion remains uniform. At high stresses under oscillatory shear, two processes can take place. One is spatial ordering (threading) of the spherical beads that does not occur in steady shear. The other is molecular interfacial slip due to high interfacial stress in samples containing fluoro‐silane treated glass beads, leading to a lower suspension viscosity than that of samples containing bare non‐treated beads.
Polymerization of conjugated dienes initiated by soluble organosodium compounds in hydrocarbon solvents
Authors: Arest‐Yakubovich Alexander A. , Pakuro Natalia I. , Zolotareva Irina V. , Kristal'nyi Energii V. , Basova Raisa V. 
Published: April 2003

AbstractPolymerization of butadiene and isoprene in hydrocarbon solvents initiated by unsolvated organosodium compounds was studied. It was found that the polymer molecular weight and the MWD are determined mainly by chain transfer to solvent and polymer, and no chain transfer to monomer was observed even in the case of isoprene. The overall polymerization rate is proportional to the concentrations of the monomer and the initiator. Apparent chain propagation rate constants were found to be 0.11 litre mol−1 s−1 for butadiene and 0.065 litre mol−1 s−1 for isoprene polymerization in heptane at 30°C. It is suggested that associated (dimeric) forms of polydienylsodium active centres play an important role in chain propagation, being responsible for a stronger chain transfer and a greater 1,2‐butadiene, or 3,4‐isoprene, unit content than in polymerization with other alkali metals.
A systematic approach to the study of multicomponent polymerization kinetics: butyl acrylate/methyl methacrylate/vinyl acetate. III. Emulsion homopolymerization and copolymerization in a pilot plant reactor
Authors: Dubé Marc A. , Penlidis Alexander 
Published: April 2003

AbstractA systematic study of the terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate (BA/MMA/VAc) is being conducted. In this third stage of the study,Parts 1 and 2: Dubé, M. A. & Penlidis, A., Polymer, 36 (1995) 587. Dubé, M. A. & Penlidis, A., Macromol. Chem. Phys., 196 (1995) 1101.
emulsion homopolymerizations and copolymerizations of the monomers comprising the BA/MMA/VAc system were performed in a 5 litre stainless steel pilot plant reactor, mainly for troubleshooting purposes and as a precursor to the detailed terpolymerization experiments to follow.First, a search for a stable emulsion recipe was conducted. At the same time, experimental procedures were established for the 5 litre pilot plant reactor along with product characterization techniques. Finally, selective emulsion homopolymerizations and copolymerizations were run for each of the three monomers and each combination of the three monomers, respectively. The polymers produced were characterized for conversion, composition, molecular weight and particle size.Although the emphasis of the experiments was to establish recipes, techniques, and procedures for emulsions terpolymerization, several useful observations were made regarding the kinetics even from these troubleshooting experiments.
Radical polymerization of acrylonitrile initiated by α‐picolinium p‐chlorophenacylid
Authors: Dixit Anju , Malik S. , Katiyar Sarvagya S. 
Published: April 2003

AbstractThe radical polymerization of acrylonitrile (AN) with α‐picolinium p‐chlorophenacylid (α‐PCPY) as initiator using carbon tetrachloride as inert solvent was investigated at 50°C. The polymerization follows ideal kinetics: the exponent values calculated for the initiator and monomer were found to be 0.5 and unity, respectively. A free radical mechanism with bimolecular termination was confirmed by the inhibiting effect of hydroquinone, a radical quencher. The rate of polymerization was a direct function of initiator (α‐PCPY) concentraction, monomer (AN) concentration and temperature. The overall activation energy calculated was 56 kJ/mol. The polymerization was favoured by polar solvents and retarded by non‐polar solvents.
Studies on permeation through polymer latex films, I. Films containing no or only low levels of additives
Authors: Steward Paul A. , Hearn John , Wilkinson Michael C. 
Published: April 2003

AbstractA range of permeation techniques were employed to investigate the transport mechanisms across polymer films cast from lattices containing either no or only low levels of water soluble leachates such as residual surfactant from polymerisation or added plasticiser essential to film formation. Hydrophilic pathways can provide a mechanism of transport, in addition to partition into and solution‐diffusion in the polymer phase. Loss of porosity by low Tg polymers on drying highlights the value of solute probes in studying film morphology.
Studies on permeation through polymer latex films, II. Permeation modification by sucrose addition
Authors: Steward Paul A. , Hearn John , Wilkinson Michael C. 
Published: April 2003

AbstractAn investigation of the effect of leachable sucrose on the permeability of polymer latex films showed that the additive can be used to vary the solute permeability in a systematic manner, as a result of increased free volume resulting from additive leaching. However, the extent of the permeability enhancement is dependent on both the glass transition temperature of the polymer and its ability to sustain porosity and prevent pore reduction by wet sintering and/or film drying, and also the compatibility of the sucrose additive with the polymer. The loading of additive dictates how readily it is leached and, hence, the presence, or not, of continuous porosity through the full thickness of film. Although continuous porosity can be conferred on the film by the sucrose leaching, the resulting porosity still greatly inhibits the permeation of electrolyte, and the film fails well before the level of porosity approaches that required for unimpeded transport.
Electrical conduction behaviour of pure and anthracene doped poly(methyl methacrylate) foils
Authors: Keller J. M. , Vyas K. D. , Dubey R. K. , Datt S. C. 
Published: April 2003

AbstractThe dark conduction current in 100 μm thick pure and anthracene doped bimetallized poly(methyl methacrylate) (PMMA) foils was measured at temperatures ranging from 333 to 383 K and filds ranging from 8 to 50 kV/cm. An attempt was made to identify the nature of the current by comparing its observed dependence on electric field, temperature and dopant concentration with the respective characteristic features of the existing theories of electrical conduction. The observed characteristics suggest that the charge carriers are generated by field assisted lowering of coulombic barriers at the traps and are conducted through the bulk of the material by a hopping process between the localized states by a Jonscher–Ansari modified Poole–Frenkel mechanism. The high value of the activation energy is considered to indicate the possibility of charge carrier species inside the polymer bulk being ionic in nature.
Photochromism of novel spirooxazine. I. Investigation of the photocoloration in polymer films and fibers
Authors: Wang Ming‐Sing , Yeh Chien‐Liang , Hu Andrew Teh 
Published: April 2003

AbstractThe photocoloration of a novel spirooxazine, 1‐[β‐(4‐trifluoromethyl benzoyloxy)ethyl]‐3,3‐dimethyl‐spiro[indoline‐2,3′‐[3H]‐naphtho[2,1‐b]‐1,4‐oxazine] (SO), doped in different polymer films and fibers was studied. The results show that photocoloration increased with increasing concentration of spirooxazine in polymer films. The photocoloration rate of spirooxazine in PMMA is faster than that in PS due to the polarity of the polymer films. A general model for the kinetics of photocoloration of spirooxazine in polymer films is proposed. The results also show that the photocoloration rate of spirooxazine in PET is faster than that in Nylon‐6 due to the crystallinity of the polymer fibers.
Moisture cure and in‐situ silica reinforcement of epoxidized natural rubber
Authors: Hashim Azanam S. , Kohjiya S. , Ikeda Y. 
Published: April 2003

AbstractEpoxidized natural rubber (ENR) was first precured with 3‐aminopropyltriethoxysilane (APS) by the normal compression molding technique. The resultant sheet was further subjected to moisture cure, via hydrolysis and condensation reactions, by soaking it in water. The moisture‐cured sample, when prepared under appropriate reaction conditions, demonstrated partial strain‐induced crystallization behavior and moderate tensile strength, as opposed to typical peroxide‐cured and sulfur‐cured vulcanizates. The suitability of the ENR–APS precured sample for in‐situ silica reinforcement by the sol–gel process, using tetraethyl orthosilicate (TEOS) as the silica precursor, was also demonstrated. Silica content as high as 36% by weight could be incorporated into the rubber, and TEOS‐to‐silica conversion of over 60% was observed. Comparative analysis with a typical peroxide‐cured sample that was subjected to the same sol–gel process indicates that the silica in the final ENR–APS sol–gel vulcanizate is chemically bound to the rubber network.
Electrically conductive TCNQ complexes of aromatic ionenes
Authors: Hochberg Gerd C. 
Published: April 2003

AbstractNew types of complex salts of 7,7′,8,8′‐tetracyanoquinodimethane with aromatic ionenes and their model compounds were prepared. The electrical conductivity and the activation energy were measured and discussed in relation to their structure. The effects of the nature of the aromatic unit, and the flexibility and rigidity of the polymer backbone were compared with the corresponding model compounds. The effects of frequency and temperature are discussed in terms of the molecular strucuture of the complex. The electroconductivity at room temperature of the 1 : 1 polymer complex salts was found to be between 2 × 10−4 and 7 × 10−5S/cm, while that of the model complex salts was between 1.3 × 10−3 and 6.3 × 10−3S/cm. The activation energy was found to be 0.14 eV on average. The limitation of the concept of polycationic complex salts of TCNQ for electrically conductive plastics for commerical application in the plastics industry is discussed.
Studies on kinetics of thermally initiated radical polymerization of divinyl ester monomers
Authors: Chandra R. , Soni R. K. 
Published: April 2003

AbstractThe divinyl ester monomers were prepared by reacting glycidyl methacrylate (GMA) with dioic acids (adipic acid, glutaric acid, succinic acid, malonic acid and oxalic acid). The reaction between the active epoxy groups of GMA and the carboxylic group of the dioic acid was catalysed by triphenyl phosphine. the curing kinetics of divinyl ester monomers were studied using benzoyl peroxide as a free radical initiator. The kinetic studies were made by differential scanning calorimetry (DSC) using the isothermal method. An explanation for the difference in the kinetic parameters with different monomers is given. A shift in the kinetic model from autocatalytic to nth order was observed in all cases. A reaction mechanism for the radical polymerization is supported by a detailed mathematical derivation and experimental results.
Multiple‐beam Fizeau fringes crossing a fibre of trilobal shaped cross‐section
Authors: Fouda I. M. , El‐Nicklawy M. M. , Hassan A. F. , Kelany A. M. 
Published: April 2003

AbstractTheoretical and experimental treatments of the shape of Fizeau fringes crossing a fibre of Trilobal‐shaped cross‐section assumed to consist of a single medium are presented. A New mathematical expression is derived and used to estimate the refractive indices and the birefringence of Perlon (polycaprolactam) fibre. The resulting data are used to calculate the polarizability per unit volume. Cauchy's dispersion constants, the isotropic refractive index and the variation of refractive index with temperature are reported. The results are in agreement with previously published data. The data are illustrated by microinterferograms.
Study of in‐situ photopolymerization of chiral liquid crystal acrylate
Authors: He Liu , Zhang Shufan , Jin Shunzi , Qi Zongneng 
Published: April 2003

AbstractThe effect of the smectic and isotropic phase on the photo‐polymerization of the chiral liquid crystalline 4‐acryloxy‐undecanyloxy‐4′‐[S(−)‐2‐methylbutyloxy]‐biphenyl (monomer (I)) was studied using FTIR. The effect of temperature on the birefringence of surface‐oriented monomer (I) and its polymer obtained by in‐situ photopolymerization was also investigated. The results show that photopolymerization in the isotropic phase proceeds at a higher rate than in the smectic phase, when monomer conversion is less than 60%; however, when monomer conversion is above 60%, the photopolymerization rate is independent of the initial phase state of monomer (I), and a highly oriented liquid crystalline polyacrylate film can be prepared by in‐situ photopolymerization of the surface‐oriented chiral acrylate (I).
Synthesis of novel grafted materials with a view to inducing biodegradability into daily‐use polymers—I
Authors: Mohanty P. , Misra P. K. , Satpathy R. K. , Mohanty N. 
Published: April 2003

AbstractTwenty polystyrene‐g‐gelatin samples were synthesised using Ce(IV) as the free radical initiator in order to make biodegradable polystyrene. Recovery of polystyrene from acid hydrolysis of the grafted sample and the appearance of new bands of gelatin at 3479 cm−1, 3235 cm−1, 1060 cm−1 and 1370 cm−1 in the IR spectrum of the grafted polystyrene sample constituted evidence of grafting, which was substantiated by evidence from 13C NMR. Thermal studies, X‐ray diffraction analysis, spectral analysis, viscosity measurements, and swelling behaviour characterised the potentially biodegradable polystyrene samples. A plausible mechanism for grafting and the probable structure of the grafted sample are suggested. Degradation studies are in progress.
Thermal and thermoelastic properties of fast extrusion furnace (FEF) carbon black loaded SBR vulcanizates
Authors: Nasr G. M. , Badawy M. M. , Gwaily S. E. , Attia G. 
Published: April 2003

AbstractThe effect of FEF carbon black as filler on the thermal capacity c, diffusivity a, and thermal conductivity λ, of styrene butadiene rubber (SBR) composites in the temperature range 300–420 K was studied. The filler strongly increases the thermal diffusivity, whilst strongly decreasing the thermal capacity and the thermal conductivity (except at high FEF content ≥80 phr).The influence of the filler on the thermoelastic behaviour of the same composites was also investigated. It was found that the thermoelastic temperature change (ΔT) increased with carbon black concentration as well as the entropy change per unit extension.
Preparation, characterization and alkali metal ion permeation through nylon 666‐g‐maleic acid membranes
Authors: Usha Kulangara , Pillai Vadasseril N. Sivasankara 
Published: April 2003

AbstractNylon 666‐g‐maleic acid membranes were prepared by 60Co γ‐ray irradiation. The membranes were characterized by measuring their thickness, tensile strength, electrical resistance, membrane potential and permselectivity. Permeability coefficients of KCI, NaCl, Na2SO4, NaOH, urea and creatinine were evaluated from dialysis experiments. The charged membranes facilitated the active transport of alkali metal ions under a pH gradient.
Active centre association in anionic polymerization. Its relation to the mechanism of polymerization of dienes in non‐polar solvents
Authors: Bywater S. 
Published: April 2003

AbstractThe dissociation mechanism suggested for lithium‐based polymerization in many cases requires a relationships between the degree of association of the active centres and the kinetic data. This connection has recently been questioned (R. N. Young, L. J. Fetters, J. S. Huang & R. Krishnamoorti, Polymer International, 33 (1994) 217). It is the purpose of the present communication to show that this questioning is not soundly based.
Synthesis and properties of poly(tetramethylene terephthalate‐co‐ethylene terephthalate)–poly(tetramethylene ether) segmented copolymers
Authors: Shi Youheng , Wu Meiyan 
Published: April 2003

AbstractA series of polyether–copolyester segmented copolymers ((PBT–PET)PTMG) based on hard segments of tetramethylene terephthalate–ethylene terephthalate copolyester (PBT–PET) and soft segments of poly(tetramethylene ether)(PTMG) was synthesized. The hard : soft segment weight ratio was 30 : 70 and the mole ratio of PBT : PET was 1 : 10; 1 : 6; 1 : 1; 3 : 1, respectively. Their mechanical properties, morphology, crystallization behavior and optical transparency were investigated and compared with poly(tetramethylene terephthalate)–poly(tetramethylene ether)(PBT–PTMG), as well as with poly(ethylene terephthalate)–poly(tetramethylene ether)(PET–PTMG), consisting of the equivalent composition ratio of hard and soft segments. It was found that the transparency could be improved by introducing a small amount of PBT into PET–PTMG through copolymerization. However, a decrease was observed in the transparency if more PBT was added. This is due to the fact that the copolymerization makes both crystallinity and crystallization rate decrease.
Cyclopolymerization of divinyl monomer with manganese (VII)—thiol redox pair
Authors: Umayavalli Manickam , Gopalakrishnan Veluchamy , Ratnasabapathy Sundramoorthy , Manickam Subramaniapillai Perumalpillai 
Published: April 2003

AbstractPolymerization of non‐conjugated divinyl monomer N,N′‐methylene bisacrylamide was studied with a novel redox pair of manganese (VII)–thiol in a homogeneous gel‐free state, under varying conditions of concentration, temperature, pH and ionic strength, and the kinetic results were interpreted by a suitable mechanistic sequence from among various possibilities. Absence of gelation is attributed to the formation of a cyclic polymer. An attempt is made to correlate the structure of the reductant–oxidant complex with the observed kinetic results.
Surface morphology and annealing of poly(butylene terephthalate)
Authors: Qudah Ali M. A. , Al‐Raheil Ismail A. 
Published: April 2003

AbstractA detailed description of the morphology and the complex melting behaviour of poly(butylene terephthalate) (PBT) annealed in the range 80–228°C is presented. Double melting endotherms can be obtained by annealing PBT in a differential scanning calorimeter (DSC). The lower endotherm corresponds to the melting of crystalline material formed at the annealing temperature in addition to some of the crystallized material reorganized during the quenching process. The upper melting endotherm results from the melting of a fraction of the original crystalline material reorganized during the DSC scan. Electron microscopy showed that the spherulitic structure over a wide range of annealing temperature below the melting point is unchanged. At high annealing temperatures, such as 228°C, electron micrographs showed that the narrow high melting peak is associated with the melting of isolated single crystals grown at that temperature.
Morphology and melting behaviour of poly(vinylidene fluoride) crystallized from the melt
Authors: Qudah Ali M. A. , Al‐Raheil Ismail A. 
Published: April 2003

AbstractThe influence of crystallization temperature on the melting behaviour and the morphology of poly(vinylidene fluoride) (PVF2) has been investigated. The DSC endotherms of PVF2 crystallized from the melt show at least two peaks. The peak areas depend on the thermal history of the samples and the heating scan rate. The area of the first peak was found to increase as the crystallization temperature or the scan rate increased. The double peak configuration was attributed to a melting–recrystallization process. Electron microscopy supports these results, for which only one type of lamella was found in the spherulitic structure.
Computer‐simulated ESR spectra of irradiated poly(olefin oxides)—effect of glass transition temperature on the ESR spectra
Authors: Murthy M. Ramakrishna , Rao B. Sanjeeva 
Published: April 2003

AbstractInvestigations on the effects of γ irradiation on poly(methylene oxide) (POM) and poly(ethylene oxide) (PEO) have been made employing electron spin resonance (ESR) spectroscopy. The ESR sextet and doublet spectra, recorded for POM and PEO, respectively, on irradition in air at room temperature are broadened as the temperature is lowered and show a reversible change in line shape with temperature. The spectra are analyzed by computer simulation, employing Lorentzian line‐shape functions and the least‐squares method of total curve fitting. The component spectra are evaluated and are assigned. Superposition of the component quartet, triplet, and doublet spectra, corresponding to the radicals ĊH3, ĊH2O , and OĊHO , respectively, together with a singlet due to the radicals ȮCH2 is considered to be the best fit to the observed spectrum for POM. The doublet spectrum recorded for PEO has been assigned to the radicals ĊHO . The reversible broadening of the spectra has been associated with the mechanism of molecular motions around the glass transition temperatures of these polymers.
Solid‐state 13C‐NMR studies of the aging of poly(vinylidene fluoride)/poly(methyl methacrylate) blends
Authors: Grinsted R. A. , Koenig J. L. 
Published: April 2003

AbstractSolid state 13C‐NMR was used to investigate the miscibility and subsequent separation of solution‐cast blends of poly(vinylidene fluoride) (PVF2) and poly(methyl methacrylate) (PMMA) with aging for a range of compositions. It was found that one amorphous phase and intimate mixing of the polymer chains in this phase existed for all compositions of the blends, even after 2 months of aging at room temperature as determined by the proton spin lattice relaxation time T1ρH in the rotating frame, and the time constant TCH for transfer of magnetization. The T1ρH is sensitive to the spatial homogeneity of the blend via spin diffusion and would indicate the presence of phases or domains in the amorphous component of the blend larger than approximately 19 Å. The TCH is proportional to the inverse sixth power of the interatomic distances needed for transfer of magnetization from proton to carbon and would be sensitive to a separation of polymer chains in the amorphous phase with aging on the order of 4–5 Å. There was an increase of the T1ρH and TCH values with aging, indicating that a subtle separation between unlike chains in the amorphous phase was occurring although a single amorphous phase was present.