bluuebunny/crossref_metadata_2025 huggingface dataset:
Sterically stabilized silica colloids: Radical grafting of poly(methyl methacrylate) and hydrosilylative grafting of silicones to functionalized silica
Authors: Ketelson Howard A. , Brook Michael A. , Pelton Robert H.
Published: April 2003

Colloidal silica sols having a narrow dispersity, prepared by the ammonia‐catalyzed hydrolysis of Si(OEt)4, were functionalized by reaction with vinyltrimethoxysilane (H2CCHSi(OMe)3) or methacryloxypropyltri‐methoxysilane (H2CCMeCO2(CH2)3Si(OMe)3. The electrostatically stabilized colloids were stable in acetone and dimethylformamide. Radical polymerization of methyl methacrylate in the presence of either type of functionalized particle led to particles with surfacegrafted poly(methyl methacrylate) (PMMA). The efficiency of polymer grafting was shown to be related to the nature of the functional groups. The PMMA‐modified, sterically stabilized particles were colloidally stable in solvents ranging from acetone to toluene but unstable in water or hexane. The vinyl functionalized silica was alternatively reacted with HSiMe2‐terminated silicones in a platinum‐catalyzed hydrosilylation. The resultant sterically stabilized particles were stable in hexane. It was thus possible to convert the unmodified silica to organo‐functionalized silica and finally to polymer‐grafted silica while maintaining colloidal stability. During the course of these modifications, the mechanism for colloidal stability changed from electrostatic to steric stabilization.
Polymerization of acrylamide and methylmethacrylate at the surface of submicron polypyrrole particles
Authors: Degobert Patrick , Henry François
Published: April 2003

This paper presents two methods of encapsulation of polypyrrole latex particles of different sizes by an insulating polymer. The first method concerns the encapsulation by inverse emulsion polymerization of acrylamide with crosslinking agent. That method is effective for the smallest particles (about 100 nm). The second method concerns encapsulation by direct emulsion polymerization of methylmethacrylate. Inhibition of polymerization occurs if potassium persulfate is used as the initiator, whereas no inhibition is observed with 4,4′ azobis 4‐cyanopentanoic acid as the initiator. These results are explained in terms of the ion‐exchange capacity of conducting polymers. This second method seems to be effective for all the sizes of polypyrrole particles. These encapsulated particles have been characterized by transmission electron microscopy, scanning electron microscopy, quasi elastic light scattering, cyclic voltametry and electrophoresis. Cyclic voltammetry recently developed on aqueous suspensions of polypyrrole particles was revealed to be the best technique because of its simplicity and speed.
Rigid aromatic fractal polyamides
Authors: Aharoni Shaul M.
Published: April 2003

The preparation of rigid aromatic, highly branched polyamides is described. Owing to the method of preparation and the chosen ratio of difunctional to trifunctional monomers, these entities are highly porous and not dendrimeric in nature. They better conform with the fractal model and are therefore called fractal polyamides (FPs). The effects of variations in the polymerization procedure, in total monomer concentration, in the ratio of amine to carboxyl groups and in the duration of the polycondensation reaction are investigated. Some characterization was performed and the results are presented and briefly discussed.
Prepation of poly(N‐isopropylacrylamide)‐grafted silica gel and its temperature‐dependent interaction with proteins
Authors: Yoshioka Hiroshi , Mikami Masato , Nakai Tomoko , Mori Yuichi
Published: April 2003

Poly(N‐isopropylacrylamide) oligomer was immobilized onto a silica gel surface. The gel adsorbed a hydrophobic protein γ‐globulin (IgG) at 37°C, however, did not adsorb IgG at 24°C. The adsorbed IgG at 37°C was adsorbed by lowering the temperatue, No adsorption of a hydrophilic protein bovin serum albumin (BSA) onto this matrix was observed at 37°C nor 24°C.
Application of poly(N‐isopropylacrylamide) with pendent β‐cyclodextrin to separation of a guest substance in an aqueous solution
Authors: Yoshioka Hiroshi , Nakai Tomoko , Mori Yuichi
Published: April 2003

Poly(N‐isopropylacrylamide) with pendent β‐cyclodextrin (PNI‐PAAm‐CD) was prepared by copolymerization of acryloyl‐β‐CD and NIPAAm. During the temperature‐induced phase separation of an aqueous solution of PNIPAAm‐CD, Toluidine Blue dye in the solution was separated into the precipitate of PNIPAAm‐CD by way of inclusion complex formation.
Mechanism of copolymerization of acrylamide with a polymerizable surfactant
Authors: Vašková Viera , Renoux Delphine , Bernard Maxime , Selb Joseph , Candau Françoise
Published: April 2003

Associating polymers have been prepared by radical copolymerization in water of acrylamide with a micelleforming cationic polymerizable surfactant. To estimate the locus of initiation, the polymerizations were carried out in the presence of initiators and radical inhibitors of various solubilities (water‐soluble or oil‐soluble), and the decay of inhibitor concentration has been monitored by electron spin resonance spectroscopy. Conversion–time curves simultaneously determined. The experimental data have been interpreted by taking into account the concentration and lifetime of the different radical species (primary radicals, oligoradicals, inhibitors), their partitioning between the micelles and the aqueous continuous phase, and the dynamics of the micellar system. Analysis of the data provided some insight into the copolymerization mechanism of these micellar systems.
Surface functionalization of polystyrene latex particles with a liposaccharide monomer
Authors: Revilla J. , Elaïssari A. , Pichot C. , Gallot B.
Published: April 2003

Emulsifier‐free latexes with immobilized carbohydrate residues have been prepared by batch or seed (co)polymerization of styrene in the presence of 11‐(N‐p‐vinylbenzyl)amido undecanoyl maltobionamide (LIMA). The critical micelle concentration and the molecular surface area of LIMA were determined by surface tension and fluorescence measurements. Batch polymerization of LIMA with styrene was first performed using potassium persulfate, proving the efficiency of LIMA as emulsifier. Seed copolymerization was then investigated using polystyrene seed particles with varying experimental conditions (especially the LIMA surface coverage). Material balance of LIMA between aqueous phase and particles was obtained by separating both phases by ultracentrifugation and it was found that the surfaceactive monomer is preferentially on or in the particle (nearly 100% in batch and at most 70% in seed copolymerization). The presence of the carbohydrate residues at the particle surface was directly evidenced by 1H‐nuclear magnetic resonance, electron spectroscopy for chemical analysis and electrophoretic mobility.
Steric stabilization of polystyrene colloids using thiol‐ended polyethylene oxide
Authors: Vidal Frederic , Guillot J. , Guyot A.
Published: April 2003

Thiol‐ended polyethylene oxide (I) has been prepared from the esterification of thioglycolic acid with monomethylether of polyoxyethylene glycol. Emulsion polymerization of styrene (and, in a few cases, methylmethacrylate as comonomer) was carried out in the presence of I using either water‐soluble azo initiator or t‐butylhydroperoxide. In the former case, bimodal particle size distribution was obtained while monodisperse latexes could be prepared in the latter case. Then a redox system was formed from I and t‐BuOOH so that I was both an initiator and a transfer agent. Good steric stabilization of the latexes was observed. The polyethylene oxide sequence of I was partly incorporated at the surface of the latex particles, but the incorporation yield remained limited (between 7 and 18%). Most of the resdue of I remained in the serum.
Preparation and characterization of cationic polystyrene latex particles of different aminated surface charges
Authors: Ganachaud F. , Mouterde G. , Delair Th. , Elaïssari A. , Pichot C.
Published: April 2003

Functionalized polystyrene latex particles were obtained either by seed particle functionalization or by the shot‐growth procedure using 2,2′‐azobis (2‐amidino‐propane) dihydrochloride as an initiator and vinylbenzylamine hydrochloride as a cationic monomer. The capabilities of both processes to produce functionalized particles in terms of functionalization yields coming from surface amino group titrations were compared. Different titration methods were performed and a new technique was introduced using fluorescamine.
Use of block copolymer surfactants in the inverse‐suspension polymerization of acrylamide
Authors: Hernández‐Barajas José , Hunkeler David J.
Published: April 2003

A comprehensive experimental investigation of the inverse microsuspension polymerization of acrylamide using an oil‐soluble initiator and a block copolymeric surfactant whose hydrophobic miety is poly(12‐hydroxystearic acid) and whose hydrophilic moeity is polyethylene oxide was carried out. It was found that the initial polymerization rate was first order with respect to molar monomer concentration, first order with respect to molar initiator concentration and zeroth order with respect to molar emulsifier concentration. Based on these experimental findings, a mechanism was proposed which includes initiation, propagation transfer to monomer and termination. It also includes transfer to impurities which are believed to be found in the surfactant. The kinetic model developed from the proposed mechanism is found to be in good agreement with the experimental conversion and weight‐average molecular weight data. Comparing with sorbitan esters of fatty acids, the copolymeric surfactant provides higher polymerization rate and very high and linear molecular weight comparable to those obtained by solution polymerization.
Interaction of proteins with polymeric latexes
Authors: Basinska Teresa , Kowalczyk Dorota , Miksa Beata , Slomkowski Stanislaw
Published: April 2003

Syntheses, modifications and properties of latexes containing polyacrolein, suitable for the covalent immobilization of proteins, are described. Results of the studies of physical adsorption and covalent attachment of human serum albumin and gamma globulins are discussed. Procedures allowing immobilization of the enzyme, horseradish peroxidase, are described. Changes in protein molecules, owing to their contact with latex particles, are analyzed. Applicability of polyacrolein containing latexes for diagnostic purposes is discussed.
Coagulation of antibody‐sensitized latexes in the presence of antigen
Authors: Ouali L. , Stoll S. , Pefferkorn E. , Elaissari A. , Lanet V. , Pichot C. , Mandrand B.
Published: April 2003

The paper describes a study of the kinetics and mechanism of the coagulation of two types of immunoassays using sensitized latexes. The positive response to the first test is based on the aggregation of the gamma globulin (IgG)‐coated polystyrene latexes in the presence of IgM rheumatoid antigen. The second test is relative to the heteroaggregation of two types of sensitized latexes induced by the presence of human chorionic gonadotropin (HCG). In the latter test, two identical polystyrene latexes bearing carboxylic acid surface groups were sensitized by covalent coupling of monoclonal antibodies specific for the αHCG determinant on one type of latex and for the βHCG determinant on the other type. Using the Coulter Counter method, the aggregate size distribution c(n) was determined as a function of the number n of elementary constituents, thus enabling calculation of the number N(t) and weight S(t) average sizes of the aggregates. The temporal variations of the average sizes were compared with typical situtions of reaction‐limited aggregation processes in order to characterize the mechanism of aggregation induced by antibody–antigen reactions.
Three‐component photopolymers based on thermal crosslinking and acidolytic de‐crosslinking of vinyl ether groups. 2. effects of acid components on photopolymer characteristics
Authors: Moon Seongyun , Yamaoka Tsuguo
Published: April 2003

The three‐component photopolymers consisting of poly(p‐hydroxystyrene) (PHS) or poly(styrene‐co‐acrylic acid) (PSA) as the binder polymer, 2,2‐bis(4‐(2‐(vinyloxy)ethoxy)phenyl)propane (BPA‐DEVE) or 1,1,1‐tris(4‐(2‐(vinyloxy)ethoxy)phenyl)ethane (THPETEVE) as the crosslinking agent, and a photoacid generator were investigated with regard to their lithographic characteristics and thermal crosslinking reactivity because of the acidity of the acid component. The thermal crosslinking rate can be represented as the pseudo first‐order reaction. The PSA copolymer with an acrylic acid unit has the higher crosslinking rate and sensitivity, and the lower activation energy. Under low baking temperatures at which crosslinking does not take place, dual‐mode resist behavior is observed.
Liquid crystalline behavior of comb–branch copolymers of di‐[6‐(4‐methoxy‐4′‐biphenyloxy)hexyl]‐2‐methylene butane‐1,4‐dioate with two non‐mesogenic chiral monomers
Authors: Cowie John M. G. , Hunter Hugh W.
Published: April 2003

A mesogenic monomer di‐[6‐(4‐methoxy‐4′‐biphenyloxy) hexyl]‐2‐methylene butane‐1,4‐dioate, has been copolymerized with non‐mesogen monomers, one racemic and one optically pure, with a view to examining the potential for using these to induce chiral liquid crystal line phases in the copolymer. This proved to be ineffective, with the copolymer exhibiting only smectic A or smectic B phases. Transition temperature–copolymer composition diagrams have been constructed for both copolymer series and their features have been contrasted. Monomer reactivity ratios have been derived for both copolymer systems.
The pockels coefficient of new polymers for nonlinear optics and its time dependence after poling, compared with dielectric measurements
Authors: Wedekind F. , Siegel J. , Gujber J. , Hummel M.
Published: April 2003

Epoxy polymers with donor–acceptor type side groups were synthesized for application in nonlinear optics. The stability of the Pockels coefficient was measured in thin films after poling. The relaxation times and their temperature dependence seem to be correlated with dielectric measurements. Guest–host systems (polystyrene and polymethylmethacrylate with dimethylaminonitrostilbene) were investigated for comparison.
Electrical conductivity of hexacene doped with iodine
Authors: Minakata Takashi , Imai Hideaki , Ozaki Masaru
Published: April 2003

Hexacene (HEX) and derivatives such as dihydrohexacene and dihydroxyhexcane quinone were synthesized and thin films of them were prepared by the sublimation method. The structure and conductivity of the films both before and after doping with iodine were studied. The doped HEX film showed the conductivity of 3 × 10−2 S/cm at room temperature, which was lower than expected since the conductivity of highly ordered pentacene was above 100 Ω−1 cm−1. The reason for the low conductivity was considered to be the disorder in molecular alignment since the HEX film showed an amorphous structure. A reversible change in the conductivity of the HEX film was observed in air and in vacuum.
Fabrication of a gas sensor using pentacene thin films as a detector
Authors: Minakata Takashi
Published: April 2003

Highly sensitive gas sensors for both acidic and basic gases were fabricated based on conducting thin films of polyacene compounds. Gas sensors formed with pentacene thin films deposited on various kinds of substrates were found to exhibit high sensitivity in detecting subppm concentrations of NO2 or Cl2 by monitoring the conductivity of the thin film. Improvements in the conductance and duration period for detection were achieved by changing the shape of electrodes and substrate. The sensors with PEN thin films initially doped with iodine could detect ppm concentrations of ammonia gas, since iodine molecules were dedoped upon exposure to ammonia, causing the reduction of the conductivity.
Photocrosslinkable second‐order nonlinear optical polymers synthesized by cationic copolymerization
Authors: Hashidate Sadahito , Nagasaki Yukio , Kato Masao , Matsuda Hiro , Nakanishi Hachiro
Published: April 2003

Photocrosslinkable second‐order nonlinear optical (NLO) polymers were synthesized from cationic copolymerization of a vinyl ether monomer bearing 4′‐nitrobiphenyl‐4‐oxy group as the NLO chromophore with a vinyl ether monomer bearing cinnamoyl group as the photoreactive moiety. To obtain a suitable poling method involving photocrosslinking, which is capable of inducing a higher and more stable second‐order nonlinear coefficient, d33, for NLO polymer films, some poling procedures were investigated. An optimized poling method was as follows. Ultraviolet (UV) irradiation is performed for 90 sec during poling at 50°C for 20 min, followed by poling at 150°C for 20 min. By using this poling method NLO polymer films exhibited a higher and considerably stable d33 value at room temperature, even though they had rather lower glass transition temperatures before photocrosslinking. Some photocrosslinking mechanism for NLO polymers investigated here were considered.
Flexural behavior of unidirectional polyethylene–glass fiber–PMMA hybrid composites
Authors: Saha Nirmal , Banerjee Amar Nath , Mitra B. C.
Published: April 2003

Unidirectional hybrid laminates based on glass fibers (GF) and high performance polyethylene fibers (PEF) were prepared with a partially polymerized methyl methacrylate (MMA) matrix at room temperature followed by heating at 55°C for the stipulated time (well below the softening point of PEF). The ultimate flexural strength (UFS), flexural modulus (FM) and interlaminar shear strength (ILSS) of the composites were determined and analyzed. An interesting observation of the study was the change in flexural behavior, which was largely dependent on the position of GF and PEF ply/plies in the compression and tension sides. When the ply/plies of PEF were at the tension side, the UFS and FM showed a higher value than that when GF plies were in the tension side of the hybrid composites. The ILSS also follows the same trend regarding the position of the GF and PEF plies.
The effect of nucleating agents on the crystallization kinetics of polypropylene
Authors: Dolgopolsky I. , Silberman A. , Kenig S.
Published: April 2003

Compositions of neat polyproylene (PP), PP–PE (polyethylene) blend and PP–PE–DBS (dibenzylidene sorbitol) were studied with respect to their crystallization kinetics by means of differential scanning calorimetry in isothermal mode. A modified Avrami equation was applied to obtain the crystallization parameters of PP, PP–PE and PP–PE–DBS. Optical and hot‐stage microscopy and dynamical analysis were used for structure determination.

Experimental results have indicated that PE addition inhibits PP crystallization rate and acts as a plasticizer, while addition of DBS changes the crystallization kinetics. A detailed study of the DBS nucleation effects indicates that owing to the high surface energy, nuclei are formed during primary crystallization, leading to a fine PP crystalline structure and improved mechanical properties.
Emulsion copolymerization of tribromophenyl maleimide with styrene
Authors: Yuan Yumin , Siegmann Arnon , Narkis Moshe , Bell James P.
Published: April 2003

Emulsion copolymerization of Tribromophenyl Maleimide (TBPMI) and styrene was conducted by semi‐batch and batch processes. The effects of monomer composition and copolymerization method on copolymerization rate, molecular weight and molecular weight distribution, latex particle size and size distribution, glass transition temperature (Tg), thermal stability and mechanical properties were investigated. A kinetic study has shown that the rate of copolymerization in the batch process increased with increasing TBPMI content in the monomer feed. For the semi‐batch polymerized samples, molecular weight decreased and molecular weight distribution increased with increasing TBPMI content in the monomer feed. For the batch polymerized samples, molecular weight also decreased but no obvious tendency was observed for the molecular weight distribution when TBPMI content increased. Compared with the batch copolymers, the semi‐batch copolymers have a higher molecular weight at the same initial monomer mixture composition. Latex particle size decreased, while particle size distribution slightly increased with increasing TBPMI content in both semi‐batch and batch latices. The semi‐batch samples exhibit only a single Tg, the value of which increses linearly with increasing TBPMI content. For the batch copolymers, two Tgs were found, reflecting a mixture of styrene‐rich and TBPMI‐rich copolymer chains. TGA results indicate that the thermal stability of the semi‐batch copolymers increased with increasing TBPMI concentration. Young's and flexural moduli increased, while tensile and flexural strengths decreased by increasing the TBPMI content for both the semi‐batch and batch specimens. The semi‐batch specimens have higher tensile and flexural strenghts than the batch ones.
Interfacial reciprocal grafting by free radical reactions in polymer blends
Authors: Seadan Manus , Lambla Morand , Narkis Moshe , Siegmann Arnon , Tzur Aliza
Published: April 2003

Recent developments in the field of reactive compatibilization of polymer blends prepared by melt processing focus on the addition of low molecular weight compounds. This work deals with in situ compatibilization through the formation of graft or crosslinked copolymers at the interface. Mixtures of semicrystalline hydrocarbon polymers have been subjected to free radical reactivity, in a co‐rotating twin screw extruder (ZSK 30) in a single step. The particular system, high density polyethylene and polyamide 6, was blended in the presence of a peroxide and a reactive bifunctional monomer, maleic anhydride. Because of a combined effect, the reaction appears to occur mainly at the interface, where the resulting grafted copolymer acts as an anchor for the final stabilization of the biphasic system. Different analytical techniques, such as differential scanning calorimetry, scanning electron microscopy and tensile testing, helped in characterizing the resulting blends and confirmed the high level of interfacial grafting and the expected improvement in mechanical properties.
Characterization and properties of carbon/PMR‐15 composites
Authors: Kim Dae Su , Lee Jae Rock
Published: April 2003

PMR (polymerization of monomer reactants) ‐15 was formulated to use as a matrix resin for high performance carbon fiber‐reinforced composite materials. Monomers for the PMR‐15 were characterized using Fourier transform infrared spectroscopy. Molecular weight change during cure was investigated using gel permeation chromatography. Thermal analysis was carried out to investigate glass transition and thermal degradation. Cure behavior of a glass/PMR‐15 prepreg was investigated using a dynamic mechanical analyzer. Flexural strength of a cured carbon/PMR‐15 composite was affected by cure temperature and pressure. The morphology of the cured carbon/PMR‐15 was affected by cure conditions as well as by the surface conditions of the carbon fibers. A scanning electron micrograph of the composite made of untreated carbon fibers showed a void‐trapped morphology.
Acrylamide/maleic acid hydrogels
Authors: Saraydin Dursun , Karadaǧ Erdener , Güven Olgun
Published: April 2003

Acrylamide/maleic acid hydrogels in the form of rods were prepared by γ‐irradiating ternary mixtures of acrylamide–maleic acid–water with 2.00–5.71 kGy γ‐rays. The influence of dose and relative content of maleic acid on the spectroscopic, thermal and mechanical properties, swelling properties, diffusional behavior of water and diffusion coefficients of hydrogel systems are examined. Acrylamide/maleic acid hydrogels were swelled in the range of 1000–2800%, While polyacrylamide hydrogels were swelled in the range of 650–700%. Water diffusion to hydrogels in non‐Fickian type diffusion. The diffusion coefficients varied from 4.5 × 10−2 to 12.2 × 10−7 cm2 sec−1.
Thermal and acid‐catalyzed reaction of bifunctional vinyl ether urethane in nonionic and ionic polymer matrices
Authors: Chen Zheliu , Ajayagohosh A. , Yamaoka Tsuguo , Sukigara Mitsunori
Published: April 2003

A bifunctional vinyl ether urethane derivative (BVU) was synthesized and characterzed. Photoresist systems consisting of BVU and a photoacid generator (PAG) along with various matrix polymers were prepared and the photoresist characteristics were evaluated. In the presence of BVU and a PAG, poly(methylmethacrylate‐co‐acrylic acid) and poly(methylmethacrylate) exhibited positive and negative tone behavior, respectively, where as poly(p‐hydroxystyrene) showed both positive and negative working properties depending on the prebake temperature of the system. The depandence of the photoresist behaviors on these matrix polymers was studied. The mechanism of the thermal and photochemical reactions was revealed.
Novel crosslinked polyurethanes with second‐order nonlinear optical effects
Authors: Liang Zhaoxi , Yan Xingzhong , Cai Zhigang , Yang Peiqing , Li Qingxing
Published: April 2003

A series of push–pull chromophores (R‐HANB) based on 4′(N,N′‐dihydroxyethyl)amino‐4‐nitro azobenzene has been designed and synthesized. R‐HANB chromophores show a strong tendency to undergo intramolecular charge transfer and show high nonlinear optical effects. During the poling process, the trimer of hexamethylene diisocyanate reacted with R‐HANB to give four various thermosetting polyurethanes simultaneously at higher temperature. The second harmonic generations (SHG) of three crosslinked polyurethane films are fairly high and stable at ambient temperature. The real‐time measurement of SHG intensity vs. poling voltage indicates that orientation of chromophores is still feasible in this crosslinked system.
Network polyester films from glycerol and dicarboxylic acids
Authors: Kiyotsukuri Tsuyoshi , Kanaboshi Masato , Tsutsumi Naoto
Published: April 2003

This paper presents information on the preparation of the network polyester films from glycerol (Yg) and aromatic dicarboxylic acids of phthalic anhydride (P), dimethyl isophthalate (I) and dimethyl terephthalate (T), as well as aliphatic dicarboxylic acids of adipic, sebacic, 1, 10‐decanedicarboxylic and 1, 12‐dodecanedicarboxylic acids, and their properties. Yg and dicarboxylic acid were polycondensed immediately before the gelation started. The prepolymers obtained were cast from DMF solution and successively post‐polymerized at various temperatures and times to form networks. The resultant films were transparent, flexible and insoluble in organic solvents. Heat distortion temperature (Th) measured by a penetration mode of thermomechanical analysis increased with increasing post‐polymerization temperature and time, and then leveled out. Th values corresponded well to the glass transition temperature (Tg) measured by differential thermal analysis (DTA). Th was 152°C, 162°C and 197°C for YgP, YgI and Yg T post‐polymerized at 270°C for 6 h, respectively. Th values of network films made from aliphatic dicarboxylic acids could not be observed until complete probe penetration occurs, as a result of thermal decomposition because the Tg is lower than room temperature. The degree of reaction estimated from the IR absorbance of hydroxyl and methylene groups was in the range of 60–80%. Two diffraction peaks appeared in the wide‐angle X‐ray scattering pattern, suggesting some ordered structure owing to the regular networks. Density decreased with increasing post‐polymerization time and temperature, in the order YgP > YgI > YgT. Network films made from aliphatic dicarboxylic acids had much lower tensile strength and Young's modulus, and greater elongation, than those made from dicarboxylic acids, as a result of the Tg being below room temperature.
Control of debromination in solution polymerisation of copper(I) 4‐bromobenzenethiolate
Authors: Archer Adrian C. , Lovell Peter A.
Published: April 2003

Debromination of poly(1,4‐phenylene sulphide), PPS, chains during formation by solution polymerisation of copper(I) 4‐bromobenzenethiolate, CBT, in quinoline and quinoline/pyridine mixtures at temperatures in the range 180–225°C has been investigated. The results are consistent with previously‐reported model compound studies and show that debromination is insignificant if the polymerisation temperatures is ≤ 200°C. Pyridine was shown not to be essential for the formation of high molar mass PPS. The optimum conditions for preparing high molar mass PPS in high yield with no significant debromination were polymerisation of CBT at a concentration of 1.0 mol dm−3 in dry quinoline under a flowing dry nitrogen atmosphere at a controlled temperature of 200°C for about 24 h.
Effects of plasma treatment on mechanical properties of rubber/cellulose fibre composites
Authors: Ahlblad Gustav , Kron Anna , Stenberg Bengt
Published: April 2003

Natural rubber materials reinforced with cellulose fibres have been studied with respect to crosslink density, tensile strength and stress relaxation. The fibres have been grafted with butadiene or divinylbenzene by plasma treatment. Chemiluminescence analysis was used to indicate the grafting on the surface of the cellulose fibres and also to estimate the effect of the plasma on the cellulose fibres. The results indicate the possibility of obtaining a surface layer on the fibres, which is a conceivable way of improving the mechanical properties of rubber composites.
Thermal and X‐ray investigations of ethylene–α‐olefin copolymers obtained with highly active supported Ti–Mg and V–Mg catalysts
Authors: Echevskaya L. G. , Zakharov V. A. , Marathe S. , Sehra J. C. , Jog J. P. , Sivaram S.
Published: April 2003

Copolymers of ethylene with propylene, butene‐1 and hexene‐1 were prepared using a titanium–magnesium (TMC) or a vanadium–magnesium catalyst (VMC). The copolymers were examined for thermal stability by TGA, melting and crystallization behaviour by DSC and crystallinity by XRD. Fractionated samples of ethylene–hexene‐1 copolymers were also similarly characterized. Results indicate that VMC produces copolymers with a higher degree of crystallinity and greater compositional homogeneity than TMC.
Cationic ring‐opening polymerization of hexamethylcyclodisilazane: General aspects and tentative mechanisms
Authors: Duguet Etienne , Schappacher Michèle , Soum Alain
Published: April 2003

The ring‐opening polymerization of hexamethylcyclodisilazane (D2NMe), initiated by methyl triflate in 1,2‐dichloroethane, forms in the first, fast kinetic step both linear polymer and cyclic dimer (D4NMe). Subsequently a slow depolymerization process occurs leading to exclusively cyclotrisilazane (D3NMe). On the basis of kinetic measurements carried out using an adiabatic calorimetric technique and complementary experiments, mechanisms of both propagation, cyclization and back‐biting reactions are proposed. The influence of the reaction temperature was also studied; it is demonstrated that, at low temperature, polymerization does not lead to cyclic oligomer formation. In such conditions, the polymerization presents a ‘living’ character.
Synthesis and characterization of poly(methyl methacrylate) star polymers
Authors: Efstratiadis Vasilis , Tselikas Giannis , Hadjichristidis Nikos , Li Jianbo , Yunan Wan , Mays Jimmy W.
Published: April 2003

Star‐branched poly(methyl methacrylate)s (PMMA) were synthesized by linking ‘living’ arms (produced by anionic polymerzation) with ethylene glycol dimethacrylate. Stars having arm molecular weights of 10000 and 40000 and between 4.9 and 18.7 branches were produced. The polymers were characterized using light scattering, size exclusion chromatography, and viscometry. It was found that well‐defined PMMA stars were obtained only at the higher (40000) arm molecular weight. The stars prepared using the lower molecular weight (c. 10000) arms contained very high molecular weight gel components.
Anionic synthesis and characterization of ω‐formyl‐functionalized polystyrenes
Authors: Quirk Roderic P. , Kuang Jianxin
Published: April 2003

ω‐Formyl‐functionalized polystyrenes can be synthesized in quantitative yield by reacting poly(styryl)lithium (Mn = 2 × 103−8 × 103 g/mol) in benzene with a 0.1−0.4 molar excess of 4‐morpholinecarboxaldehyde followed by methanol termination and precipitation into methanol. Narrow molecular weight distribution ω‐formyl‐functionalized polystyrenes were characterized by hydroxylamine end‐group titration, thin layer chromatography and both 1H and 13C NMR spectroscopy. The mechanism of the functionalization was studied by trapping the tetrahedral α‐amino alkoxide intermediate with diphenylphosphinic chloride.
Methacrylate‐based block ionomers I: Synthesis of block ionomers derived from t‐butyl methacrylate and alkyl methacrylates
Authors: Deporter Craig D. , Long Timothy E. , McGrath James E.
Published: April 2003

Diblock and triblock copolymers of t‐butyl methacrylate (tBMA) with 2‐ethylhexyl methacrylate (EHMA) and n‐hexyl methacrylate were prepared via alkyl lithium initiation and sequential addition techniques in THF at −78°C. The tBMA blocks were quantiatively and selectively hydrolyzed to afford poly(methacrylic acid) (PMAA) blocks which were then neutralized with alkali metal bases to form block ionomers. The unhydrolyzed copolymers had a phase mixed morphology as evidenced by thermal analysis while the hydrolyzed and neutralized polymers were multiphase materials. The carboxylic acid and ioncontaning triblock copolymers formed gels in nonpolar solvents which could be disrupted by the addition of polar additives. Certain carboxylic acid and ioncontaining EHMA/tBMA diblock copolymers also showed this behavior. The triblock ionomers did not show thermoplastic flow prior to degradation, except at the lowest ionic content studied (2%).
Fibre reinforced composites of multifunctional epoxy resins
Authors: Jagadeesh K. S. , Siddaramaiah
Published: April 2003

Glass and carbon fibre reinforced epoxy composites were fabricated for N,N,N′,N′‐tetraglycidyl‐4,4′‐diaminodiphenyl methane (TGDDM) and its formulated systems with tri‐ and di‐functional reactive epoxy diluents using 30% diaminodiphenyl sulphone (DDS) as a curing agent. The epoxy laminates were evaluated for their physical, chemical and mechanical properties [at room (26°C) and high (100°C) temperatures]. A marginal increase (<20%) in the mechanical properties of CFRP was found compared with GFRP laminates. Incorporation of epoxy diluents altered the mechanical properties of the composites significantly. The incorporation of triglycidyl‐4‐aminophenol diluent to TGDDM systems resulted in an improvement in mechanical properties of about 2–6%.
Influence of the chemical modification of phenoxy resin on its miscibility with poly(2‐vinyl pyridine)
Authors: Eguiburu J. L. , de Ilarduya A. Martinez , Iruin J. J. , Fernández‐Berridi María J.
Published: April 2003

The influence of the chemical modification of the hydroxyl groups of phenoxy resin (PH) by benzoate, acetate and methoxy groups on its miscibility with poly(2‐vinyl pyridine) (P2VPy) is investigated. Both DSC and FTIR results permit the definition of three distinctive regions: up to 40% modification all 50/50 blends are miscible; between 40 and 55% modification all blends present partial miscibility and at higher than 55% modification the blends are totally immiscible. Specific interactions between the hydroxyl groups of PH and the amine groups of P2VPy are put forward as an explanation for these observations.
Influence of γ‐irradiation on proton spin–lattice relaxation of SBR used as antirads and its ESR investigation
Authors: El‐Sayed Adly H. , El‐Aziz Y. Abd , Rammadan T. , Badran B. M. , Medycki W. , Pislewski N.
Published: April 2003

Proton spin–lattice relaxation time t1 was measured on SBR samples with carbon black or kaolin filler using modified linseed oil. The NMR pulse technique at 90MHz was used in the temperature range from 180 to 400 K. The temperature dependence of t1 indicates that samples filled with carbon black have similar molecular dynamics to the standard unfilled SBR samples. The activation energy for the motion of the main chain for these samples amounts to 16.4kJ/mol. Samples containing linseed oil modified with para‐toluidine showed an activation energy of about 14.6kJ/mol and were not affected by γ‐irradiation. Values of the minimum relaxation time tmin1 were increased by γ‐irradiation in comparison with a standard SBR sample. ESR measurements carried out at room temperature by means of an X‐band spectrometer indicated that unidentified radicals within the rubber were formed during its mastication with vulcanizing additives. The ESR spectra did not change during the vulcanization process. Samples filled with carbon black showed a broadening of the ESR line; this is consistent with the increase in the electrical conductivity.
Electrical and electromagnetic shielding behavior of laminated epoxy–carbon fiber composite
Authors: Ramadin Y. , Jawad S. A. , Musameh S. M. , Ahmad M. , Zihlif A. M. , Paesano A. , Martuscelli E. , Ragosta G.
Published: April 2003

This paper reports results on the electrical properties of laminated epoxy composite containing 25 layers of carbon fibers in the form of mats. The dependence of the activation energy (calculated from DC resistivity measurements) on temperature reveals two independent conduction processes. The AC impedance is independent of the applied frequency below 75°C, and the real componet of the dielectric constant is also independent of temperature at high frequencies. The determined shielding effectiveness is dominated by the insertion loss. The observed optimum shielding effectiveness occurs at 30 mm spacing and applied frequency 9 GHz.
Dielectric investigation of isotropic and anisotropic solutions of hydroxypropyl cellulose in dioxan
Authors: Moteleb M. M. Abdel , Naoum M. M. , Shalaby M. M. , Saad G. R.
Published: April 2003

The dielectric behaviour of hydroxypropyl cellulose in dioxan has been studied at 10–50°C over a range of concentration of 10–55 wt% to include the isotropic and anisotropic phases. The study showed that the loss maximum ε″max magnitude of polarization ε0 − ε∞ relaxation time 1/2πfm degree of broadening of the absorption curves 1–h or α, and the mean‐square dipole moment 〈gμ2〉, steadily increase with concentration up to 42 wt%, above which a rapid decrease takes place. This indicates that the isotropic solution transforms to an anisotropic solution with a smaller mean dipole moment. The critical concentration is realized to be temperature invariant. This was evidenced by measuring the refractive index of solutions covering the same concentration and temperature ranges.
Copolymerization of styrene on to cellulose activated by corona
Authors: Bataille P. , Dufourd M. , Sapieha S.
Published: April 2003

The corona discharge technique was explored as a means of forming chemically active sites on cellulose surfaces. Paper thus treated was brought into contact with the reaction medium, a styrene–methanol mixture.

The corona discharge was generated between two flat circular electrodes separated by a quartz disk. Scanning electron microscope analysis and wettability studies indicated that a hydrophobic film coated the cellulosic fibers.

The molecular weights of both the homopolymer and the copolymer were characterized by GPC. Two peaks for grafted copolymer were observed, the first having about the same average molecular weight as the homopolymer, and the second having a molecular weight of about ten times the first fraction.

A polymerization mechanism is proposed.
Transient currents in the discharge mode in pure and malachite green doped polymethylmethacrylate films
Authors: Khare P. K. , Singh Ranjeet
Published: April 2003

The transient currents in the discharge mode in polymethylmethacrylate (PMMA) and malachite green doped PMMA films measured as a function of temperature (363–383 K) and field strength (2.0 ×103‐2.0 × 104 V/cm) have been found to follow the Curie–von Schweidler law, characterized by different slopes in the short and long time regions. Various mechanisms which may be responsible for the time‐dependent transient currents of pure and malachite green doped PMMA films are discussed. The effect of doping with malachite green on the discharge current indicates the formation of molecular aggregates.
Microstructure and compatibility of PVDF/PS blends in the presence of PVA
Authors: del Rio C. , Acosta J. L.
Published: April 2003

This research refers to a compatibility study of binary and ternary PVDF blends with PS and PVA by means of the determination of the polymer polymer interaction parameter χ12 calculated from melting point depression analysis of the blends. In addition, a PVDF spherulite growth rate study was conducted in the binary and ternary blends with PS and/or PVA. The nucleation factor is determined by applying the Lauritzen–Hoffman theory.

The results obtained show PVA to be capable of compatibilizing PVDF/PS systems when present in concentrations of 30 vol%.
The effect of polymers on the crystallisation of n‐alkanes from solution, part 2. Mode of action of fumarate–vinyl acetate copolymers
Authors: Davidson Iain G. , Cameron G. Gordon
Published: April 2003

The amount of octadecyl fumarate‐vinyl acetate (C18FVA) copolymer which co‐crystallised with dotriacontane from dodecane solution was measured by infrared and electron spin resonance (ESR) spectroscopy. It was found that the magnitude of the slow‐motion component in the composite ESR spectra of the system below its cloud point did not accurately reflect the amount of polymer which had co‐crystallised with the dotriacontane. ESR studies of isolated samples of the co‐crystallate showed the C18FVA to be less tightly bound than in the bulk polymer, suggesting that the polymer molecules are adsorbed on to the surface of the dotriacontane crystals.
Interaction of collagen with polypyrrole in the production of hybrid materials
Authors: Li Hwee Chze , Khor Eugene
Published: April 2003

A series of collagen–polypyrrole hybrid materials have been synthesized by the chemical polymerization of pyrrole using FeCl3 as initiator in the presence of soluble collagen. The black color of the resulting materials indicates the presence of polypyrrole while collagen was verified by amino acid analysis of the hybrids. Collagen incorporation into the hybrid was found to be a function of pyrrole concentration used in the polymerization. When the concentrationof pyrrole was high, the collagen loading was low and vice versa. This inverse relationship was also found in the hybrids' electrical conductivity. A 26% collagen content in the hybrid gave a conductivity of 1.4 S cm−1 while a 4% collagen gave a higher value of 62.4 S cm−1. Thermogravimetric data suggest that the two polymers exist in the hybrid as a blend. The nature of the interaction of the components in the hybrid is believed to be strong since collagen could not be extracted despite denaturation with sodium dodecylsulfate.
Hardness of weakly and ‘late’ cross‐linked polymethylmethacrylate and its relationship to chain statistics
Authors: Gündüz Güngör , Kirkin Metin
Published: April 2003

The hardness of ‘late’ and weakly crosslinked polymethylmethacrylate was determined experimentally. As the time of the addition of the cross linker to the polymerizing polymer increases, the hardness first increases, passes through a maximum and then decreases. This change can be expressed by an asymmetric curve. The change of hardness is expressed in terms of a theoretical equation based on the distribution of chains. Some scaling relationships were obtained.
Dilute solution properties of poly(2‐methoxycyanurate) of bisphenol F and bisphenol A
Authors: Patel G. M. , Patel N. K. , Kansara Sujata
Published: April 2003

Poly(2‐methoxycyanurate) of bisphenol F and bisphenol A (PMCBFA) was synthesized and fractionated by a fractional precipitation method. The fractions were characterized by viscometry, osmometry and gel permeation chromatography. The Mark–Houwink–Kuhn–Sakurada (MHKS) parameters were established in four solvents and at four different temperatures. The unperturbed dimensions and their coefficients in different solvents were computed using the Stockmayer–Fixman excluded volume theory. From the solution study it was found that PMCBFA is highly flexible. This may be due to the ether linkage present in the main chain.
A rheological model for polymer blends based on the concentric multilayer approach. I. Homogeneous polymer blends
Authors: Chu Line‐Hwa , Chiu Wen‐Yen , Tseng Hsieng‐Cheng
Published: April 2003

The melt rheological behavior of polymer blends was investigated by means of a capillary rheometer. The systems chosen for study were blends of polystyrene (PS) with different molecular weights and blends of polymethylmethacrylate (PMMA) with different molecular weights. A modified concentric multilayer model was proposed to correlate the rheological properties of the polymer blends with the composition and shear rate. The agreement between the calculated values and the measured ones is satisfactory.
Interpenetrating polymer networks: A review on synthesis and properties
Authors: Gupta Nidhi , Srivastava A. K.
Published: April 2003

A review containing 83 references on the chemistry aspects (mechanism and structure–property relationships) for IPN synthesis is presented.
Thermodynamics of random copolymers of N‐vinylcarbazole and 4‐alkylstyrenes
Authors: Privalko V. P. , Arbuzova A. P. , Korskanov V. V. , Zagdanskaya N. E.
Published: April 2003

Random copolymers of N‐vinylcarbazole (VC) and alkylstyrenes with variable molar content of VC (first series) or variable size of alkyl substituent (second series) were characterized by the heat capacity measured at normal pressure in the temperature interval 203–523 K, as well as by measurements of specific volume and thermal diffusivity in the temperature interval 303–523 K and in the pressure range 30–100 MPa. It was established that the increase of thermal mobility of chain repeating units with the molar ratio of hexylstyrene (in the first series) or with the alkyl chain length (in the second series) manifests itself as a shift to lower temperatures of the glass transition temperature, as well as an increase of heat capacity, thermal diffusivity and effective number of external degrees of freedom per chain repeating unit from the Simha–Somcynsky reduced equation of state. The inadequacy of the simple diad additivity scheme for a quantitative description of structure–property relationships for the copolymers studied is emphasized.
Relaxation in PMMA films doped with aniline derivatives for nonlinear optics
Authors: Zheng Guo‐qi , Xu Yue‐lian , Wang Wei‐li , Feng Zhun‐jie , Wang Xian‐shan , Wen Jian‐xun
Published: April 2003

Dynamic viscoelastic spectra, thermally stimulated current, optical absorption spectra and second harmonic generation (SHG) intensity have been measured in poled films of PMMA doped with aniline derivatives. These experiments have indicated that the volume, axial ratio and dipole moment of the dopant molecules, and doping level have significant influences on the stability of SHG of the poled polymers. A mechanism based on free volume theory is proposed which interprets the experimental observations satisfactorily.
Photoinitiation of polymerization of styrene by oxotris(dimethyl dithiocarbamato) vanadium(V)
Authors: Aliwi Salah M. , Abdullah Salah M.
Published: April 2003

Oxotris(dimethyl dithiocarbamato) vanadium(V) [VO(S2CN(CH3)2)3] sensitizes the polymerization of styrene when irradiated by light of λ = 365 nm at 25°C. Under the experimental conditions employed, no retardation occurs, and the rate of initiation is independent of monomer concentration. The mean values of the quantum yield of iniiation (ϕi) and polymerization (ϕo) are 2.85 × 10−3 and 6.72 respectively. Spectroscopic analysis shows that initiation occurs predominatly through scission of the N,N‐dimethyl dithiocarbamate ligand (—SC(S)N(CH3)2) with reduction of vanadium(V) to (IV), and VO (S2CN(CH3)2)2 is the final photolytic product.

A reaction mechanism is proposed based on an intramolecular photoredox reaction which leads to the primary formation of SC(S)N(CH3)2 radicals and a vanadium(IV) chelate complex. The rellevant kinetic parameters are evaluated. The polystyrene produced shows a photoactivity when irradiated with UV‐light.