bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of the degree of acetylation of o‐cresol resin on its molecular conformation in solution
Authors: Yamagishi Tada‐Aki , Kumagai Hiroyuki , Hasegawa Toshiaki , Nakamoto Yoshiaki , Ishida Shin‐ichiro 
Published: April 2003

Abstracto‐Cresol‐formaldehyde resin (OC) and five kinds of acetylated OC (AC‐X‐OC; X is the degree of acetylation) were prepared. The Θ‐temperature for each resin was determined by means of the Shultz‐Flory method, and their molecular conformations in both tetrahydrofuran (THF) and Θ‐solvent were estimated from the values of the exponents in the Mark–Houwink–Sakurada equations. The effect of the degree of acetylation on the exponent was negligible in THF, but was remarkable in Θ‐solvent. In THF, the molecular chains of these resins are relatively extended, because the hydrogen bond between phenolic hydroxyl groups is loosely formed. In Θ‐solvent, however, the molecular conformation is compact and the resins are considered to form a pseudo cross‐linked network structure through inter‐ and/or intra‐molecular hydrogen bonds. The Mark–Houwink–Sakurada equation for AC‐100‐OC in 2‐ethoxyethanol at 92.0°C was found to be [η]θ = 0.0773 M̄0.50n, where [η]0 is the limiting viscosity number under the Θ‐condition, and M̄n is the number‐average molecular weight. The unperturbed dimension, (〈r20〉/M̄n)1/2, 〈r20〉 being the unperturbed mean square end‐to‐end distance, for AC‐100‐OC was found to be 0.659×10−8 cm g−1/2 mol1/2.
Preferential interactions of poly(N‐vinyl‐2‐pyrrolidone) in the binary mixture water/CdCl2
Authors: Gómez Clara , Blanco M. Dolores , Olmo Rosa , Lozano Rafael , Teijón José M. 
Published: April 2003

AbstractThe poly(N‐vinyl‐2‐pyrrolidone)(PVP)(2)/water(1)/CdCl2(3) ternary system has been studied by viscometry, densimetry and atomic absorption spectrophotometry. In this system a preferential adsorption of Cd2+ at all solvent compositions studied and a conformational transition at 4mM of salt, the concentration at which a preferential adsorption minimum of Cd2+ in exhibited, are observed. The PVP/Cd2+ bound molar ratio is 0·23. CdCl2 behaves as a salting‐in agent for the macromolecule. The binary solvent mixture is thermodynamically more favourable at salt concentrations greater than 10 mM of CdCl2.
Stabilization of photo‐induced radicals in hematoporphyrin‐IX‐doped chitosan film
Authors: Kaneko Hiroaki , Shirai Akihiro , Takahasi Kiyohisa , Miura Yoshiaki , Nitta Katsutoshi , Nishimura Shin‐Ichiro , Nishi Norio , Tokura Seiichi , Tsutsumi Akihiro 
Published: April 2003

AbstractInduction and stabilization of free radicals were investigated in hematoporphyrin‐IX (Hp)‐doped chitosan (Hp‐Ch) film by electron spin resonance (ESR) following photo‐irradiation. Induced radicals were more stable in chitosan and 6‐O‐carboxymethyl chitin films than in carboxymethyl cellulose and sodium alginate films. Hydroxyl groups on D‐glucosamine residues in chitosan are suggested as participating in accepting radicals, since spin trapping was absorbed in ESR spectra of Hp‐Ch film by the use of oxygen sensitive spin trapping reagent. An induced circular dichroism spectrum was observed only for Hp‐doped chitosan film over a range 360–450 nm among seven pairs of polymers and dyes; it is suggested that Hp molecules are arranged parallel along the carbohydrate backbone of chitosan, resulting in the highest acceptance of photo‐induced radicals in the polymer film.
Polyurethanes from renewable resources. III: synthesis and characterisation of low molar mass polytetrahydrofuran diols and their glucosides
Authors: Donnelly Michael J. 
Published: April 2003

AbstractPolytetrahydrofuran diols are polyurethane precursors obtainable from carbohydrate feedstocks. A range of commercial diols of different molecular weights were selected and supplemented by synthesised diols of lower molecular weights. To increase the carbohydrate content of derived polymers each diol was reacted with 1 or 2 moles of glucose and converted to a glucoside in high yield using a solution reaction. Complex products resulted, which approximately may be represented by mono‐ or bisglucoside structures. The parent diols and the glucosides were characterised using a wide range of techniques including acetylation equivalent weight, functionality towards diisocyanate, GPC, DSC, GLC, IR, HPLC, viscosity determinations and various wet chemical analyses. Relative to the parent diols, the properties of the glucosides (such as high viscosity, wider range of functionality towards MDI, and the relationships between transition temperatures and (diol) molecular weight) are explained as due to the rigidity and large free volume of the terminal glucose unit, its potential for increasing hydrogen bonding, and its ability to cause disruption of polytetramethylene oxide chain ordering.
Dielectric investigation of isotropic and anisotropic solutions of cellulose acetate in dioxane
Authors: Naoum M. M. , Moteleb M. M. Abdel , Shalaby M. M. , Saad G. R. 
Published: April 2003

AbstractThe dielectric and optical characteristics of a sample of cellulose acetate (DS = 2.45) in dioxane solutions were studied at 10–50°C of concentration 10–50 wt% to include both isotropic and anisotropic phases. The study showed that the loss maximum, εmax″, magnitude of polarization, (ε0 − ε∞), static dielectric constant, ε0, time of relation, (2πfm)−1, and refractive index, nD, steadily increase with concentration up to the critical concentration (41 wt%) and then decrease. The mean‐square dipole moment, 〈gμ2〉, decreases steadily up to the critical concentration then remains nearly constant, indicating that the isotropic solution changes to anisotropic, with smaller mean‐square dipole moment. Comparison between the results of cellulose acetate (CA) and those of hydroxypropyl cellulose (HPC) reveals that, at the critical concentration in dioxane, the cholesteric structure of HPC possesses a greater mean‐square dipole moment with higher temperature coefficient than does CA. The activation energy of the relaxation process for hydroxypropyl cellulose is higher, indicating a greater intrachain interaction compared with cellulose acetate.
Observations by DSC on bound water structure in some physically crosslinked hydrogels
Authors: Liu Yan , Huglin Malcolm B. 
Published: April 2003

AbstractLinear, compositionally homogeneous copolymers containing 23–62 wt% N‐vinyl‐2‐pyrrolidone (VP) were prepared by a semi‐continuous copolymerisation with methyl methacrylate (MMA) in the absence of chemical crosslinker. Films cast from solution in chloroform were swollen in water at various temperatures (T) within the range 283–343 K. The total water content (11–80 wt%) of the resultant hydrogels at swelling equilibrium, as well as its subdivision into freezing and non‐freezing water components, were measured and found to be dependent on copolymer composition and T. The network structure of these hydrogels is considered to arise from a combination of normal VP–water interactions with physical crosslinking due to hydrophobic MMA sequences, and the novel, albeit only semi‐quantitative, findings are discussed on this basis.
Synthesis, and NMR and thermogravimetric characterisation of block polymers of methyl methacrylate and methacrylic acid
Authors: dos Santos Cláudio G. , Jenkins Aubrey D. , Walton David R. M. 
Published: April 2003

AbstractBlock polymers of methyl methacrylate and methacrylic acid have been prepared using the technique of enolate‐initiated anionic polymerisation, employing trimethylsilyl methacrylate as a precursor for the methacrylic acid component. The structure of the product has been characterised by infra‐red and NMR spectroscopy, and by thermogravimetric analysis.
Electrodeposition of polyaniline and polyaniline composites from colloidal dispersions
Authors: Eisazadeh H. , Spinks G. , Wallace G. G. 
Published: April 2003

AbstractThe voltammetric properties of colloid dispersions of polyaniline have been studied. It has been found that with the use of appropriate oxidants, spherical polyaniline colloids with well defined voltammetric characteristics can be obtained.It has also been found that these colloids can be electrocoagulated to form coatings by imposition of a negative potential. Novel ‘Composite films’ can also be deposited from mixtures of colloids and show unique properties.
Interfacial effects on the rheological behavior of HDPE/EPDM/CB composites
Authors: Zhu Jin , Ou Yu‐Chun , Feng Yu‐Peng 
Published: April 2003

AbstractInvestigation of the effects of an interfacial modifier on the rheological behavior of binary high‐density polyethylene (HDPE) composites showed that the interfacial modifier significantly changed the melt state behavior of HDPE/carbon black (CB) composites. This suggests that the interfacial adhesion between the CB surface and the HDPE is significantly improved by the incorporation of the interfacial modifier. Although the dispersion of filler in the matrix was improved, HDPE was also temporarily crosslinked by the CB Particles in the melt due to the strong interfacial interaction.For HDPE/ethylene propylene diene rubber (EPDM) composites, incorporation of CB caused limited change of the melt state behavior. Addition of interfacial modifier to the HDPE/EPDM/CB composite also resulted in a change of the melt state behavior compared with the unmodified composite, but the effect was not so pronouced as that in the HDPE/CB composites. The difference is well explained by the different phase structure. A core–shell dispersed phase structure with the filler as a core and rubber as a shell was formed in the modified composite, with the crosslinking effect predominating in the dispersed phase, while a separate filler and rubber dispersed phase predominated in the unmodified composite. The conclusion is further supported by the solid state dynamic mechanical analysis in a previous paper and SEM micrographs in this paper.
Network characteristics of homopolymer and some copolymers of poly(2‐hydroxyethyl methacrylate)
Authors: Perera Don I. , Shanks Robert A. 
Published: April 2003

AbstractSoluble poly(2‐hydroxyethyl methacrylate) and copolymers of 2‐hydroxyethyl methacrylate with n‐butyl acrylate and 2‐hydroxypropyl acrylate of varying compositions were synthesised by solution polymerisation. The polymers were characterised by dilute solution viscometry and shear viscosity. Crosslinked membranes were prepared from these polymers by introducing crosslinks in solution state through the reaction with 1,6‐hexamethylene diisocyanate at a number of different crosslinker concentrations. The membranes swollen in dimethylformamide and water were characterised by performing equilibirium swelling measurements and calculating polymer volume fraction, the molecular mass between crosslinks (M̄c) and equilibrium water content (EWC) at 25°C. The calculation of M̄c used an expression developed by Peppas & Lucht for equilibrium swelling. This is a modified equation of the original Flory–Rehner expression, that allows non‐Gaussian distribution of chain lengths. The variation of M̄c with crosslinker concentration and copolymer composition is discussed in terms of structural and molecular characteristics of these highly crosslinked networks.
Studies on dynamic behaviour and flow properties of HDPE/EPDM blends by torque rheometer
Authors: Chandra R. , Mishra S. , Parida T. R. 
Published: April 2003

AbstractThe effect of blend ratio on the crosslinking characteristics and dynamic elastic properties of HDPE/EPDM blends was studied by a torque rheometer. The crosslink density (a measure of tensile strength) first increases and then decrease with increase in EPDM content. The dynamic elastic property (a measure of impact strength) also showed a peculiar trend. Both studies showed that less than 40 parts loading of EPDM gave the best mechanical properties. In another study the flow activation energy was calculated by temperature programming, which gave the value of processing temperatures (cold mixing, hot mixing).
Mechanism of nickel catalysed dehalogenative step polymerization of aryl dibromides
Authors: Siove Alain , Aboulkassim Aïcha , Faïd Karim , Ades Dominique 
Published: April 2003

AbstractDehalogenative polycondensation of 3,6‐dibromo‐N‐alkylcarbazoles was catalysed by a Ni(O)‐based complex generated in N,N‐dimethylacetamide by electroreduction of NiBr2/2,2′‐bipyridine. The process involves three different reaction steps, which are successively: electrolysis of Ni(II) to Ni(O); insertion of the latter into a CBr bond of monomer leading to CNiBr* active species; dehalogenative coupling between active species and monomer yielding oligomers. From the kinetics of electrogeneration of the catalytic system in absence of monomer, a first‐order reaction was determined. Insertion and coupling reactions were found to be second‐order and comparison of the values of the corresponding rate constants clearly showed that coupling is the rate‐determining step of the process. Simultaneous size exclusion chromatography and cyclic voltammetry measurements were carried out in the course of the electrosynthesis of poly(N‐alkylcarbazole)s. The change in the molar mass population distribution as a function of electrolysis time revealed a step polymerization process, while showing a termination of the chain growth due to the occurrence of monobrominated species. The study of the effect of the [monomer]/[catalyst] ratio on the molar mass population change indicated that the coupling of active species (Ni(O)‐activated monomer) is responsible for the chain growth.
Preparation of bis(chloroformate)s for use in cyclization reactions
Authors: Brunelle Daniel J. , Bonauto David K. , Shannon Thomas G. 
Published: April 2003

AbstractCyclic oligomeric carbonates are prepared by a hydrolysis/condensation reaction from aromatic bis(chloroformate)s. Three methods for convenient preparation of bis(chloroformate)s have been developed: (1) use of diethylaniline to scavenge HCl, in a modification of an earlier procedure; (2) low pH, low temperature interfacial condensation of bisphenols with phosgene; and (3) use of Ca(OH)2 in interfacial condensation with phosgene. Reaction parameters which control formation of monomeric bis(chloroformate)s versus higher oligomerization include temperature, pH, and rate of phosgene addition. For water‐soluble bisphenols such as hydroquinone, the phase ratio of water to CH2Cl2 can also be important.
Benzocyclobutenyl functionalized polymers of cyclotrimerized terminal diynes: synthesis and crosslinking
Authors: Gentsy George G. , Farona Michael F. 
Published: April 2003

AbstractThe monomers 1,13‐tetradecadiyne, 1,11‐dodecadiyne, 1,9‐decadiyne and 1,7‐octadiyne were cyclotrimerized, using niobium pentachloride as the catalyst, in the presence of 1,5‐hexadiyne, which co‐cyclotrimerizes to give a benzocyclobutene (BCB) capping group. Molecular weights of the BCB‐capped oligomers were in the 3100–8000 range, with fairly narrow polydispersities. The oligomers were characterized by 1H NMR and IR spectoscopy, along with GPC and DSC studies. DSC studies on the end‐capped oligomers show that each exhibits an exotherm around 260°C, indicative of the formation of carbon–carbon bonds in a crosslinking reaction. The final, crosslinked materials may be regarded as thermosetting thermoplastics, since they are hard at room temperature and soft at 250°C.
About the various types of transfer reactions in the cationic polymerization of isobutyl vinyl ether
Authors: Leleu J.‐M. , Bernardo V. , Polton A. , Tardi M. , Sigwalt P. 
Published: April 2003

AbstractFor isobutyl vinyl ether (IBVE) polymerizations made in the presence of large concentrations of an electron donor such as ethyl acetate (EA), e.g. 0.5 M, evidence for transfer reactions of zero order in monomer concentration has been given earlier. In the present paper, the changes in the transfer processes according to the ester concentration are examined. Polymerizations were made under vacuum at 0°C in toluene. Solvent and monomer were dried over sodium films. Two initiating systems were used.Initiation with trityl tetrachloroaluminate (2.5 × 10−5 −2 × 10−4 M) gave very fast reactions, which were stopped at various yields and showed that transfer of first order in [M] is the main transfer reaction (with ktrM/kp at 0°C). The addition of a small amount of EA (5 × 10−2M) lowers the reaction rate considerably but leads only to a small reduction of ktrM/kp (to 5·6 × 10−4).Initiation with isobutyl‐1‐chloroethylether (IBCE) and an excess of aluminium trichloride ([AlCl3]/[IBCE] ≃ 10) was made in the presence of increasing amounts of EA. This lowers the propagation rate (first order in [M]). For [M]0/[I]0 ratios lower than 300, the linearity of M̄n with yield is observed (‘living’ polymerization) but a strong deviation occurs for higher [M]0/[I]0. The linear increase with reaction time of the concentration [N] of macromolecules resulting from transfer is in agreement with a preponderant transfer of zero order in [M]. Transfer to monomer is considerably reduced. The relative importance of transfer of zero order in [M] increases with [EA], and it involves mainly ethyl acetate.The reduction of direct transfer to monomer in the presence of high concentrations of ethyl acetate is explained by a propagation mechanism involving monomer solvated cationic active species, in equilibrium with inactive species solvated only by ethyl acetate.
Size exclusion and adsorption column chromatographic studies on functionality distribution of HTPB
Authors: Panicker Sreelatha S. , Ninan K. N. 
Published: April 2003

AbstractAdsorption column chromatography and size exclusion chromatography have been used to determine the functionality distribution of hydroxyl terminated polybutadiene (HTPB), a modern solid propellant binder. The resin after conversion to 3,5‐dinitrobenzoyl ester was separated into various fractions on a silica column. The fractions were analysed using a dual detector (UV and differential refractive index) analytical gel permeation chromatograph. The functionality of each fraction calculated from the chromatogram showed a continuous increase with increase in the molecular weight. The adsorption chromatography method is unable to fractionate the polymer into fractions with specific functionality. All the fractions have molecules ranging from monofunctional to multifunctional ones and therefore the apportionment method followed in the conventional adsorption chromatography method yields conflicting results.
Dielectric investigation of the molecular dynamics of blends (II): polymers with dissimilar molecular architecture (PS/TMPC blend)
Authors: Mansour Ashraf A. , Madbouly Samy A. 
Published: April 2003

AbstractThe molecular dynamics of polystyrene/tetramethyl polycarbonate (PS/TMPC) blends were investigated using dielectric spectroscopy in the frequency and temperature ranges 10−2−107 Hz and 50–220°C, respectively. Blends with different compositions, namely 12.5, 25, 50, 75 and 87.5 wt% PS/TMPC were found to be compatible over the entire composition range and showed one glass relaxation process corresponding with the transition observed by calorimetric measurements. It was found that neither the kinetics or the distribution of relaxation times of the local process observed in pure TMPC were affected by blending. This fact implies that the local environment of the segments is not changed upon blending. Furthermore, these blends showed that the blending of TMPC with weakly polar polystyrene does not cause any change in the dipolar interaction of the TMPC segments, so that the relaxation strength varies linearly with composition. It is concluded that the polymeric chains of the TMPC and PS are not mixed at a segmental level, but at a higher structural level lying somewhere between segmental and molecular. This conclusion is in good agreement with that obtained in the case of blends composed of polymers with similar molecular architecture.
Synthesis of end‐functionalized polymer by means of living anionic polymerization. 4. Synthesis of polyisoprene and polystyrene with epoxy termini by reaction of their anionic living polymers with 2‐bromoethyloxirane
Authors: Takenaka Katsuhiko , Hirao Akira , Nakahama Seiichi 
Published: April 2003

AbstractIn order to synthesize ω‐epoxy‐functionalized 1,4‐polyisoprene ω‐epoxy‐ and α,ω‐diepoxy‐functionalized polystyrenes, anionic living polyisoprene and polystyrene were allowed to react with excess amounts of 2‐bromoethyloxirane in THF at −78°C. The resulting polymers were analysed by SEC, 1H and 13C NMR spectroscopy, and thin layer chromatography with flame ionization detection (TLC–FID). Both mono‐ and di‐epoxy terminated polymers of controlled molecular weights (2.5 × 103−2.6 × 104 g/mol) and of narrow molecular weight distributions were obtained quantitatively with high functionalities.
Thermal properties of polypropylene/rice husk ash composites
Authors: Fuad M. Y. Ahmad , Mustafah J. , Mansor M. S. , Ishak Z. A. Mohd , Omar A. K. Mohd 
Published: April 2003

AbstractIncorporation of rick husk ash (RHA) fillers into polypropylene affected some of the thermal properties of polypropylene composites. Addition of the black rice husk ash (BRHA) filler raised the thermal degradation temperature while maintaining the oxidative stability. The thermal degradation temperature of the white rice husk ash (WRHA) composites was found to be independent of filler loading but the oxidative stability deteriorated with increasing filler content. DSC studies indicated that both white and black RHA fillers act as weak nucleation agents and increase the degree of crystallinity of polypropylene by a small margin. Addition of the RHA fillers reduced the linear thermal expansion coefficient of the composites. Dynamic mechanical studies showed that the RHA composites with higher filler content have higher storage modulus. Tan δ curves of the composites indicated that WRHA filler increased the damping property while the BRHA filler had an opposite effect.
Aminolysis reaction of poly(N‐4‐methylphenylitaconimide) and its graft copolymerization
Authors: Qiu Kun Yuan , Zhao Tong 
Published: April 2003

AbstractPolyitaconimide and copolymers of itaconimide were transformed to macromolecules having diamido pendent groups via an aminolysis reaction. The polymers obtained were cast into films, which were then graft copolymerized with acrylamide (AAM) using ceric ion as an initiator.Radical homopolymerization and copolymerization of N‐4‐methylphenylitaconimide with methyl acrylate or ethyl acrylate were carried out at 60°C in benzene; high molecular weight polymer and copolymers (M̄n = 104–105) were obtained. The resulting polymer and copolymers were reacted with n‐butylamine in order to produce polymers possessing a pendent 4‐tolylcarbamoyl group (4‐CH3C6H4NHCO‐), which can significantly promote the acrylamide (AAM) graft copolymerization initiated with ceric ion.Transparent films of the polymers were graft copolymerized with AAM in the presence of ceric ion at 45°C. The formation of graft polymers was verified by water absorption percentage, XPS and SEM.
Thermal gelation of poly(vinyl chloride)
Authors: Basan Satilmis̨ , Karadağ Erdener 
Published: April 2003

AbstractThe dynamic and isothermal gelation points of poly(vinyl chloride) (PVC) were determined using spectrophotometric and viscometric techniques. Four different PVC samples, with viscosity‐average molar masses of 70 000, 90 000, 106 000 and 141 000, were used. The dynamic thermal gelation points of PVC samples heated to temperatures between 120 and 280°C were found to be between 232 and 236°C. Isothermal gelation times of PVC (M̄v = 106 000) heated at 170, 180, 190 and 200°C were determined as 345, 177, 78 and 37 min., respectively.An inverse relationship between the tendency to dynamic and isothermal gelation with increase in molar mass of PVC samples was found. On the other hand, the tendency to isothermal gelation of PVC increases with raising temperature.