bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of oxidation treatment of carbon powders on the cure kinetics of amine cured tetrafunctional epoxy resins
Authors: Andres M. A. , Miguez R. , Corcuera M. A. , Mondragon I.
Published: April 2003

A tetraglycidyl 4,4′‐diaminodiphenylmethane (TGDDM) type tetrafunctional epoxy resin containing carbon powders was cured with the stoichiometric amount of a tetrafunctional curing agent, namely m‐phenylenediamine (mPDA). Carbon powders were oxidised with air or nitric acid. The influence of carbon powders on curing of the resin was followed by dynamic mechanical analysis, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Gelation and vitrification times were determined as a function of the variations of dynamic properties. The evolution of viscoelastic modulus during curing of the different mixtures showed that untreated carbon powder clearly accelerated the kinetics of curing whilst oxidation of carbon powders could remove their catalysing effect. These results were confirmed by monitoring the changes in conversion of epoxy and amine groups during cure using the FTIR technique. DSC experiments also showed the influence of carbon powder as a catalyst and the loss of the catalysing effect as a consequence of chemical treatment.
A reinvestigation of electrolyte effects in the emulsion polymerisation of styrene
Authors: Said Ziad F. M.
Published: April 2003

The effects of adding potassium chloride in concentrations below that required to coagulate the latex to recips of emulsion polymerisation of styrene have been investigated using different concentrations of potassium octadecanoate, which has a low critical micelle concentration (CMC), and potassium dodecanoate, which has a moderately high CMC. At relatively high concentration of octadecanoate the final particle size is significantly increased; the rate of polymerisation is initially increased but later retarded. The effects of increasing micelle size and increased rate of coalescence are dominant. At lower concentration of this emulsifier, the rate is reduced from the onset of interval II.

With dodecanoate, concentrations of electrolyte up to 0.3 M accelerate the rate. No significant change in the particle size was observed up to 0.2M electrolyte, thereafter it slightly increased. The increase in micellar concentration can only partially account for these effects. It is believed that the increase in the amount of solubilised monomer inside the micelles, and later inside the latex particles, and the resistance to coalescence (because of the favourable adsorption mechanism of this emulsifier) may account for these observations.

With both emulsifiers, electrolyte reduces the induction period and latices with narrow particle size distributions are produced.
Polycondensation of tetramethyldisiloxane 1,3‐diol catalyzed by trifluoromethanesulfonic acid
Authors: Bischoff R. , Sigwalt P.
Published: April 2003

The kinetics of polycondensation of tetramethyldisiloxane 1,3‐diol (HD2OH) have been followed by stopping the reaction at increasing times (by neutralization of the acid and trimethylsilylation of the silanol end‐groups). Analyses of the linear and cyclic oligomers and of the higher polymer have been made by gas–liquid chromatography and by steric exclusion chromatography. At the beginning of the reaction (e. g. between 1 min and 1 h) the main products are linear oligomer H(D)2nOH and D4 (formed by cyclization of HD4OH). There are only very small amounts of large cycles. Linear high polymer is then formed slowly together with increasing amounts of cycles D5, D6, D7, …, formed by backbiting reactions. After 24h, the yield of D4 is 40–50% and that of linear polymer 40–30% (Mpeak × 104–105). With disilanol concentration 0.45–0.9 mol liter−1 and CF3SO3H concentration about 10−3 mol liter−1, the reaction is very rapid during 1–2 min and the medium becomes heterogenous with the formation of an inverse water emulsion. The reaction then slows down considerably, most of the hydrated acid being trapped in the water droplets. Silanol consumption is second order in [SiOH] and first order [TfOH]o. Polymerizations made in polar and non‐polar solvents have similar rates, which however increase moderately in the order toluene<1,2‐dichloro‐ethane<dichloromethane, this corresponding to an increasing solubility of the hydrated acid in these solvents. Polycondensation occurs in the organic phase near the interface, either by esterification of silanol followed by heterccondensation or by homocondensation catalyzed by the hydrated acid (or both).
Structure and morphology of small diameter electrospun aramid fibers
Authors: Srinivasan Gokul , Reneker Darrell H.
Published: April 2003

Very small diameter fibers of poly(p‐phenylene terephthalamide) (PPTA) ranging in diameter from 40nm to a few hundreds of nanometers were made by the electrospinning process. The fibers have a circular cross‐section, are birefringent and stable at temperatures greater than 400°C. Electron diffraction patterns obtained from both as‐spun and annealed fibers show meridional and equatorial reflections demonstrating order in the material. The crystal structure and morphology of the fibers were characterized using bright and dark field electron microscopy, electron diffraction and atomic force microscopy.
Synthesis of porous hydrogel structures by polymerizing the continuous phase of a microemulsion
Authors: Bennett Darrell J. , Burford Robert P. , Davis Thomas P. , Tilley Heath J.
Published: April 2003

A series of microemulsions have been formulated, with 2‐hydroxyethyl methacrylate (HEMA) or HEMA/water/propanol mixtures as the continuous phase and methylcyclohexane as the discontinuous phase. The effect of surfactant type was investigated with the utilization of both anionic and nonionic surfactants. The microemulsion continuous phase was polymerized by UV radiation and a thermal post‐cure. The resultant polymers were extracted to remove the discontinuous phase and the surfactant. On swelling, the majority of the polymers became opaque, although transparent PHEMA hydrogels were synthesized with an improved equilibrium water content (EWC). The cause of opacity was shown by field emission scanning electron microscopy (FESEM). The breakdown in the microemulsion on polymerization is caused by unfavourable interactions between the PHEMA and the stabilizing surfactants causing agglomerization of the discontinuous phase. All the hydrogels were found to have higher water retention than PHEMA, with EWCs of up to 70%. The modified polymers also demonstrated an increased rate of water diffusion into the matrix. A preliminary study of oxygen permability revealed that a significant improvement had been made over standard PHEMA membranes. The porous structure of the PHEMA gels has been shown to be dependent on the type of surfactant used during synthesis.
Dielectric investigation of the molecular dynamics in blends: polymers with similar molecular architecture (TMPC/PC blend)
Authors: Mansour Ashraf A. , Madbouly Samy A.
Published: April 2003

Broad band dielectric spectroscopy was used in the investigation of the molecular dynamics and compatibility of tetramethyl polycarbonate/polycarbonate (TMPC/PC) blends. Frequency scan measurements in the range 10−2−10−5 Hz were carried out in the temperature range 50–220°C for several blends with different compositions, namely, 0, 12.5, 25, 50, 75, 87.5 and 100 wt% of TMPC. The results obtained show that these two polymers are ideally compatible over the entire composition range. The blends reveal only one common glass process. The dielectric relaxation strength and the common glass transition temperature, Tg, were found to vary linearly with composition. Moreover, it was found, surprisingly, that blending has no effect on the distribution of relaxation times of the common glass process of the blends. Furthermore, neither the kinetics (relaxation frequency at a certain temperature) nor the distribution of relaxation times of the local process were influenced by blending. It is concluded that the polymeric chains of the different components are not miscible on a segmental level although the blend exhibits only one glass transition temperature.
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

o‐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

The 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

Induction 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

Polytetrahydrofuran 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

The 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

Linear, 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

Block 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

The 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

Investigation 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

Soluble 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

The 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

Dehalogenative 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

Cyclic 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

The 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

For 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

Adsorption 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

The 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

In 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

Incorporation 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

Polyitaconimide 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

The 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.
Effect of ammonium derivatives of oligoamidephosphates on the vulcanization characteristics and mechanical properties of some rubber compounds. 2. Styrene butadiene rubber compounds
Authors: Vladkova Todorka G. , Arnaudova Rumyana V.
Published: April 2003

SBR compounds containing ammonium derivatives as neutral analogues of the oligoamidephosphates were studied with respect to their vulcanization characteristics and mechanical properties. Several differences between the effects of the neutral ammonium derivatives and the oligoamidephosphates were discovered, which may be connected with the different pHs of these products. As in the case of isoprene rubber compounds, the neutral products showed increased efficiency in comparison with the oligoamidephosphates. They offer the possibility of four‐fold reduction of the optimum cure time and partial replacement of the base sulphenamide accelerator. All SBR compositions containing neutral ammonium derivatives (NADs) were relatively well crosslinked and had cure characteristics and mechanical properties equal to, or better than, the corresponding compositions without neutral ammonium derivatives, even in the cases when the NAD amount was predominant. The results of our experiments give reason to assume that NADs participate in the vulcanization process with the formation of a different number of chemical bonds of various types. The NADs probably affect some physical interactions also.
Synthesis and characterisation of ternary polymer electrolytes with enhanced miscibility and high conductivity
Authors: Paulmer R. D. A. , Kulkarni A. R.
Published: April 2003

This paper reports the synthesis of amorphous polymer electrolytes. Polymer–salt complexes in the ternary system were prepared by mixing two polymers, namely poly(oxyethylene) and poly(oxypropylene glycol), with sodium iodide. This three component system is represented on a ternary pseudophase diagram. The ternary compositions are completely amorphous in a certain composition range and the composition POE–12%POPG–Nal with O/Na = 10 exhibited record high conductivity of 2 × 10−4 (Ω cm)−1 at ambient temperature. Formation of the amorphous electrolyte and the enhanced miscibility of the polymers were analysed using differential scanning calorimetry, X‐ray diffraction and ionic conductivity studies. The cation was found to play a major role in enhancing the miscibility of the polymers.
New amphiphilic poly(butadiene)‐graft‐poly(ethylene oxide)s
Authors: Decher Heribert , Stadler Reimund
Published: April 2003

Amphiphilic graft copolymers with a poly(butadiene) backbone and poly(ethylene oxide) side chains were synthesized by grafting isocyanateterminated poly(ethylene oxide) on to partially hydroxylated poly(butadiene). The graft copolymers are water soluble if the fraction of hydrophilic poly(ethylene oxide) exceeds 50 wt%. Solutions of graft copolymers in water and tetrahydrofuran were studied by static light scattering and viscosity measurements. By dynamic light scattering in solution it was shown that the graft copolymers form clusters.
New fluorinated polysiloxanes containing an ester function in the spacer—II. Surface tension studies
Authors: Beyou Emmanuel , Bennetau Bernard , Dunoguès Jacques , Babin Pierre , Teyssié Dominique , Boileau Sylvie , Corpart Jean‐Marc
Published: April 2003

The surface tensions of fluorinated polysiloxanes prepared by hydrosilylation of unsaturated perfluoroalkyl esters derived from undecylenic acid [CH2CH(CH2)8COOCH2CH2RF, with RF = C6F13, C8F17, and C8F17(CH2)10COOCH2CH2CHCH2] by methylhydrodimethylsiloxane copolymers of various SiH contents have been measured. The critical surface tensions, γc, and the solid surface tensions, γDs, were deduced from n‐alkane and water contact angle data. They decrease as the perfluoroalkyl graft content of the copolymers increases. Some of them, which are in the range of the lowest surface tension fluoro polymers known, are observed when the fluorinated segments are self‐organized at the interface, i.e. when the polymers are mesomorphous or crystalline at room temperature.
Influence of dynamic cyclic extension on the electrical conductivity of fast extrusion furnace (FEF) black loaded rubber vulcanizates
Authors: Nasr G. M. , Darwish K. A. , Khairy S. A. , Hassan H. H. , Ateia E.
Published: April 2003

The influence of dynamic cyclic extension on the electrcal conductivity (σ) of 100 parts FEF carbon black loaded rubber (NR and SBR) vulcanizates was studied. The conductivity showed an initial rapid decrease with increasing cyclic strain amplitude, indicating a probable breakdown of the carbon black structure, owing to the masking of carbon particles by insulating rubber layers.

The conduction mechanisms in these composites in terms of both the number of strain cycles and the strain amplitude were also studied. In addition, the temperature coefficient of conductivity was calculated for different amplitudes. It was greatly affected by the magnitude of the strain amplitude.
Behaviour of catalase immobilised on poly(acrylonitrile)‐g.co‐hydroxyethyl methacrylate when used in a continuous system
Authors: Piedade A. P. , Gil M. H. , Cavaco M. C. , Andrade M. E.
Published: April 2003

Several poly(acrylonitrile)‐g.co‐hydroxyethyl methacrylate graft copolymers were prepared using gamma irradiation (60Co). The influences of the monomer concentration and the time of irradiation on the level of grafting were studied. Some of the graft copolymers obtained were characterised and used for the covalent immobilisation of catalase using two different methods of activation of the support.

The enzyme/support systems obtained were characterised and the best selected to be used in a first approach for the study of the deterioration of a hydrogen peroxide solution in a continuous system.
Monomer sequence length distributions of hard segments of linear segmented poly(urethane–urea)s 2: computer simulation by the Monte Carlo method
Authors: Hanahata Hiroyuki , Kamide Kenji
Published: April 2003

An attempt was made to calculate, by the Monte Carlo method, monomer sequence length distributions of the hard segment (MSLDH) within a linear segmented poly(urethane–urea) (PUR) synthesised by the prepolymer method in which an isocyanate‐terminated prepolymer. A…A, an unreacted monomer diisocyanate, BB, and a diamine as chain extender, XY, are reacted to form PUR. MSLDH is governed by the molar ratio of [A…A]/[BB] and is dramatically affected when three kinds of unequal reactivity associated with the reactants are significant simultaneously; the induced asymmetry, the penultimate effect of an NCO group, and the induced asymmetry of an amino group. By applying the above simulation technique, the unequal reactivities are estimated in both the prepolymerisation and polymerisation reactions based on methylenebis(4‐phenylisocyanate), MDI, poly(tetramethyleneoxide), PTMO, and ethylenediamine, EDA. In addition, the effect of the one‐shot method instead of the prepolymer method on MSLDH is also examined.
Skinned polymeric membranes. Approach to the mechanism of formation of surface holes
Authors: Addad J. P. Cohen , Icard B. , Pellicioli L.
Published: April 2003

It is shown quantitatively that the formation of holes through the skin of membranes, prepared by the quick immersion in water of polyetherimides in solution in N‐methylpyrrolidone, is governed by the solvent mobility. The surface pattern observed by videomicroscopy exhibits a characteristic distance between neighbouring holes (≃5 μm) which is a linear function of D−1s; Ds is the solvent diffusion coefficient in the polymeric solution, measured using a pulsedfield gradient NMR technique. The dependence of this distance on the solvent concentration in water is also characterized.
New poly(amide–imide)s syntheses. 17. Preparation and properties of poly(amide–imide)s derived from N‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)‐phenyl]phthalimidine, trimellitic anhydride, and various aromatic diamines
Authors: Yang Chin‐Ping , Lin Jiun‐Hung
Published: April 2003

A dicarboxylic acid (1) bearing two phthalimide rings was prepared by the condensation of N‐phenyl‐3,3‐bis[4‐(4‐aminophenoxy)phenyl]phthalimidine and trimellitic anhydride. A new family of poly(amide–imide)s having inherent viscosities of 0.65–1.65 dl/g was prepared by the triphenyl phosphite activated polycondensation of the diimide–diacid 1 with various aromatic diamines in a medium consisting of N‐methyl‐2‐pyrrolidone (NMP), pyridine, and calcium chloride. All the resulting polymers showed an amorphous nature and were readily soluble in polar solvents such as NMP and N,N‐dimethylacetamide. The soluble poly(amide–imide)s afforded transparent, flexible, and tough films. The glass transition temperatures of these polymers were in the range 249–340°C and the 10% weight loss temperatures were above 545°C in nitrogen.
Morphology and melting behaviour of poly(ethylene terephthalate) crystallized from the glassy state
Authors: Qudah Ali M. A. , Al‐Raheil Ismail A.
Published: April 2003

The influence of annealing conditions on the morphology and melting behaviour of poly(ethylene terephthalate) (PET) was studied. PET annealed under isothermal conditions often shows double melting endotherms depending on the annealing temperature (Ta) and the heating rate of the calorimeter. It was found that the morphological structure and the lower melting peak depend strongly on the annealing temperature, Ta. The increase of the lower melting peak temperature with Ta is due to an increase of the lamellar thickness within the spherulitic structure and to a higher crystallite perfection.
Counterion association to cationic polyelectrolytes in methanol/water mixtures
Authors: Barraza Raúl G. , Rios Hernán E.
Published: April 2003

The effect of the nature of the medium on the chloride and bromide condensation to a cationic polyelectrolyte was studied. Methanol/water mixtures were used as solvent in order to vary continuously the properties of the medium. The counterion–polyion interaction was studied by the determination of the Eisenberg interaction parameter (f*) by means of electrical conductivity measurements. Results indicate that f* parameters increase while the limiting electrical conductivity is rapidly decreasing. This apparently anomalous phenomenon is interpreted as a preferential solvation of the polyelectrolyte which brings about a conformational change, as revealed by the intrinsic viscosity behavior of the solutions. This change could induce an increase in the average distance between charges without further dissociation, which could explain the observed behavior of the f* parameter. It is concluded that the actual dielectric constant which governs the polyion–counterion interaction in the polyelectrolyte domain is not the bulk dielectric constant.
Segmental mobility model for diffusion of gases in polymers
Authors: Stuk L. G. F.
Published: April 2003

Diffusion of small molecules in polymers is described quantitatively in terms of segmental mobility processes. The diffusion coefficient depends on a diffusive jump length, which is characteristic of the polymer, and a jump frequency, which is equated to the segmental mobility rate. The presence of a particular solute increases mobility of the surrounding polymer segments by a predictable amount, which is related to the partial molar volume of the solute. The theory is fit to experimental diffusion data, and partial molar volumes are calculated from the fitting parameters. Good agreement with experimental partial molar volumes is obtained.
Toward a prediction of the phase behavior of polyamide blends
Authors: Hu Jiangbin , Painter Paul C. , Coleman Michael M. , Krizan Timothy D.
Published: April 2003

As we have reported recently, the application of association models has provided a theoretical basis for the calculation of the free energy changes and phase diagrams of binary polymer blends in which hydrogen bonding plays a significant role. Here we report theoretical calculations of spinodal phase diagrams of a series of polyisophthalamide‐polyether blends and compare the predictions with experimental observations of the miscibility of these polymer blend systems. The general agreement between theory and experiment is very encouraging and has important ramifications to discussions of polymer‐induced crystallnity, the minimum number of hydrogen bonding sites necessary to ensure significant molecular mixing, and the effect of hydrogen bonding on the breadth of “miscibility windows.”
Transport properties of a thermotropic liquid‐crystalline polyester
Authors: De Candia F. , Renzulli A. , Vittoria V. , Roviello A. , Sirigu A.
Published: April 2003

Transport properties of a thermotropic liquid‐crystalline polymer with the mesogenic group in the main chain were analyzed. Different samples were examined as films obtained by pressure molding and rapid quenching to 0°C. Thermal and transport parameters of the quenched films were measured. The results show that the isotropization enthalpy and sorption coefficient are interdependent, while the diffusion coefficient is substantially constant in all the samples analyzed. These results suggest that the permeable component behaves in the same way in the different samples but is present in different amounts, the transport phenomena occurring in amorphous, or less ordered, interphase regions within impermeable mesomorphic and crystalline domains.
Radiation effects on poly(1‐chloro‐1‐alkynes)
Authors: Tang Ben‐Zhong , Masuda Toshio , Higashimura Toshinobu , Yamaoka Hitoshi
Published: April 2003

The γ‐radiolysis behavior of poly(l‐chloro‐1‐alkynes)
\[
[\rlap{‐‐} ({\rm CCI} = {\rm CR}\rlap{‐‐} )_n ;{\rm R} = n ‐ {\rm alkyl}]
\]
greatly changed with the length of alkyl group and with the presence or absence of oxygen. When γ‐irradiated in air, poly(l‐chloro‐1‐hexyne) (R = n‐C4H9) decomposed to oligomers; its Gs value was as large as 5.4. When irradiated in vacuum, this polymer partly gelled. In contrast, poly(l‐chloro‐1‐decyne) (R = n‐C8H17) partly gelled even by irradiation in air. A high‐dose irradiation of this polymer in vacuum resulted in the quantitative formation of a gel. The polymers irradiated in air contained carbonyl and hydroxyl groups, indicating the participation of oxidation reaction. Comparison with their thermolysis leads to a conclusion that these Cl‐containing polyacetylenes are radiation‐sensitive irrespective of their high thermal stability.
Concentration dependence of the flory‐huggins interaction parameter of a polymer blend as determined by small‐angle X‐ray scattering experiments
Authors: Koch T. , Strobl G. R.
Published: April 2003

Direct determination of the Flory‐Huggins interaction parameter χ of a polymer blend by small‐angle x‐ray scattering experiments is possible on the basis of the random phase approximation, if absolute intensities are measured. The usually superposed void scattering has to be properly accounted for. Investigations on a series of blends of polystyrene and poly(styrene‐co‐bromostyrene) yielded χ dependent upon the blend composition. χ shows only slight variations. Scattering data also give the radii of gyration of the two components in the blend.