bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution. I. THF–CCI4 system
Authors: Matyjaszewski Krzysztof , Kubisa Przemysław , Penczek Stanisław 
Published: April 2003

AbstractPolymerization of THF in CCl4 solvent was initiated with 1,3‐dioxolan‐2‐ylium eations with AsF6−, PF6−, and SbF6− anions as well as with esters of fluorosulfonic and trifluoromethanesulfonic acids. With these esters polymerization proceeds with a marked acceleration period, due to slow initiation. The corresponding rate constants of initiation and their dependence on the polarity of the THF/CCl4 mixture were determined. The rate constant of propagation on the macroion‐pairs (kp±) of the polytetrahydrofurylium cation with AsF6−, PF6−, and SbF6− and CF3SO3−, anions was found to be independent in CCl4 solvent on the anion structure and given by the expression: kp± = 2.93 × 10−2 exp {−4.7 × 103/T} at [THF]0 = 8.0M. This constant depends on the polarity of the polymerization mixture, and at 25°C for the THF‐CCl4 system, kp± = 1.78 × 10−2 exp {−4.9/D}; thus, in CCl4 at [THF]0 = 8.0M, and at 25° kp± = 4.0 × 10−21/mole‐sec. In the polymerization with derivatives of CF3SO3H (able to form the corresponding macroester) the overall polymerization rate is much lower than that with complex anions because of the reversible conversion of the macroion‐pairs into the macroester (internal return). The macroester is much less reactive than the macroionpair (102–103 times) in the monomer addition reaction. At [THF]0 = 8.0M and at 25°C, 96.5% of the growing species exists in the macroester form.Polymerization of THF initiated with derivatives of CF3SO3H is a subject of a strong special salt‐effect. At a sufficiently high ratio of [AgSbF6] to [I]0, where the initiator I is C2H5OSO2CF3, the overall polymerization rate is equal to that observed for the polymerization of THF on the macroion‐pairs, since the internal return within the triflate ion‐pair (the macroester formation) is eliminated and polymerization proceeds on the macroion‐pairs with SbF6‐ anions exclusively.
Critical surface tension of poly(vinyl butyral) and poly(vinyl benzal) multilayers and its relation to their surface orientation. I. Effect of surface pressures during deposition
Authors: Ueno M. , Meguro K. 
Published: April 2003

AbstractCritical surface tensions γc of poly(vinyl butyral) and poly(vinyl benzal) multilayers built up by the Langmuir‐Blodgett method were measured with polyhydric alcohols and n‐alkanes. The γc values of both polymer multilayers increased with increasing pressures of the piston oils used to control pressures of polymers on the water surface during deposition. The γc value of poly(vinyl butyral) multilayers built up to lower pressure of the piston oil was approximately consistent with a crystalline hydrocarbon surface, while the γc value of the multilayer built up to higher pressure of the piston oil was approximately consistent with a—CH3 rather than a CH2 CH2 surface. All results for γc values of poly(vinyl benzal) multilayers were very close to the γc value of benzene ringrich surface. The γc value of the multilayer built up to lower pressure of the piston oil almost coincided with the γc value for amorphous polystyrene, while the γc value for the multilayer built up to higher pressure of the piston oil was in fair agreement with γc for an aromatic ring edge in the crystalline state. Values of γsd, the dispersion force contribution to the surface free energy of multilayers calculated by Fowkes' relation, were in fair agreement with the corresponding observed γc values, respectively. It is concluded from these measurements that orientations and surface structures in both polymer multilayers are affected by pressure change of piston oils. The properties on monolayers of two polymers at a air‐water interface and on barium stearate multilayers are also presented.
Effects of solvent on the free‐radical copolymerizabilities of pyridazinones with styrene
Authors: Matsubara Yoshio , Enyo Kooji , Yoshihara Masakuni , Maeshima Toshihisa 
Published: April 2003

AbstractFree‐radical copolymerizations of N‐methylpyridazinone (I) and N‐phenylpyridazinone (II) with styrene (M1) were carried out in various solvents. The copolymerization rates were found to increase linearly with increasing viscosities of the reaction mixtures. Monomer reactivity ratios were strongly affected by the reaction media. This might be due to solvation of the carbonyl group of the pyridazinone ring, because linear relationships between log 1/r1 and vc=o of the pyridazinones were obtained. It was also found that monomer concentration influences these copolymerizabilities.
Photopolymerization of methyl methacrylate by use of a quinoline–bromine charge‐transfer complex as the photoinitiator
Authors: Ghosh Premamoy , Mitra Partha Sarathi 
Published: April 2003

AbstractPolymerization of MMA was carried out in presence of visible light (440 nm), quinoline‐bromine charge‐transfer complex being used as the photoinitiator. The initiator exponent was observed to be 0.5 up to 0.014 M initiator concentration; when chloroform was used as the solvent, the monomer exponent was found to be unity. The polymerization was inhibited in presence of hydroquinone but little inhibitory effect was observed in the presence of air. An average value of k2p/kt for this photopolymerization system was found to be (1.08 ± 0.22) × 10‐2. Kinetic and other evidence indicates that the overall polymerization takes place by a radical mechanism.
Thermosetting diphenyl sulfone‐based maleimides
Authors: Kwiatkowski G. T. , Robeson L. M. , Brode G. L. , Bedwin A. W. 
Published: April 2003

AbstractThermosetting arylimides were prepared by reaction of sulfone ether diamines with maleic anhydride followed by chemical imidization of the intermediate polyamic acid with acetic anhydride/sodium acetate. These arylimides could be thermally cured to afford heat stable systems possessing high glass transition temperatures (Tg) and moderate to high modulus plateaus above the Tg, depending upon the molecular weight between maleimide sites. The addition type curing process alleviates problems associated with the fabrication of other polyimide systems, since volatiles are not liberated and lowviscosity, high‐solids solutions can be prepared in common organic solvents. Thermal, mechanical, adhesive and fabrication characteristics are reported for the sulfone‐based arylimides, which indicate utility in spectrum of high‐temperature applications.
Self‐crosslinkable polymers. I. Copolymerization of glycidyl methacrylate with 2‐vinylpyridine and 2‐vinyl‐5‐ethylpyridine
Authors: Tanaka Yoshio , Atsukawa Morishige , Shimura Yukio , Okada Akira , Sakuraba Hideki , Sakata Tokuji 
Published: April 2003

AbstractA soluble and self‐crosslinkable linear copolymer with pendant epoxy and pyridyl groups was obtained from glycidyl methacrylate (M1) and 2‐vinylpyridine (M2) or 2‐vinyl‐5‐ethylpyridine (M2) by the action of azobisisobutyronitrile. The monomer reactivity ratios were determined in tetrahydrofuran at 60°C: r1 = 0.510, r2 = 0.620 with 2‐vinylpyridine and r1 = 0.57, r2 = 0.62 with 2‐vinyl‐5‐ethylpyridine. These were consistent with the calculated values with the reported Q and e values for these monomers. The intrinsic viscosities of the copolymers with 2‐vinylpyridine and with 2‐vinyl‐5‐ethylpyridine were found to be 0.17–0.19 and 0.26–0.38, respectively, in tetrahydrofuran at 30°C; they were independent of the copolymer composition. The copolymers were amorphous, had no clear melting points, and became insoluble crosslinked polymers under heating without further addition of any curing agents.
Study on radiation‐induced polymerization of vinyl monomers adsorbed on inorganic substances. I. Radiation‐induced polymerization of styrene adsorbed on several inorganic substances
Authors: Fukano Kazuyuki , Kageyama Eiichi 
Published: April 2003

AbstractThe radiation‐induced polymerization of styrene adsorbed on silica gel, white carbon, silicic acid anhydride, zeolite, and activated alumina was carried out to elucidate the effect of properties of inorganic substances on the polymerization. The rate of adsorbed state polymerization on these inorganic substances was very fast in comparison with that of bulk‐state polymerization. The amount of unextractable polymer depends on the specific surface area and chemical compositions of these inorganic substances. Inorganic substances which contain aluminum as a component element are more likely to be grafted than those which consist of SiO2alone. The molecular weight and molecular weight distribution of unextractable polymer and extractable polymer differ from one another in each inorganic substance. In case of silicic acid anhydride, unextractable polymer has smaller molecular weight than extractable polymer. These results suggest that unextractable polymer cannot be extracted due to chemical bonds with the inorganic surface.
Studies on reactions of the N‐phosphonium salts of pyridines. XIV. Wholly aromatic polyamides by the direct polycondensation reaction by using phosphites in the presence of metal salts
Authors: Yamazaki Noboru , Matsumoto Makoto , Higashi Fukuji 
Published: April 2003

AbstractPoly‐p‐benzamide of high molecular weight (ηinh = ∼ in H2SO4) was obtained by the direct polycondensation reaction of p‐aminobenzoic acid (p‐ABA) by means of diphenyl and triaryl phosphites in N‐methylpyrrolidone (NMP)‐pyridine solution containing lithium and calcium chlorides. Molecular weight of polymer varied with the amount of these salts, showing maximum values at the concentration of about 4 wt‐% of LiCl or about 8 wt‐% of CaCl2 in the reaction mixture. The reaction temperature at around 80°C gave a polymer of the highest viscosity. The polycondensation reaction was also affected by monomer concentration, solvents, and tertiary amines like pyridine. Similarly, aromatic polyamides with high molecular weight (ηinh values up to 1.34 in H2SO4) were prepared from isophthalic acid and aromatic diamines, whereas terephthalic acid gave only low‐viscosity polymers.
Investigations on poly(vinyl chloride). II. Pyrolysis of chlorinated polybutadienes as model compounds for poly(vinyl chloride)
Authors: Iida Takeo , Nakanishi Motoharu , Gotō Kunio 
Published: April 2003

AbstractThe pyrolysis of chlorinated polybutadienes (CPB) was investigated by using a pyrolysis gas chromatograph. CPB corresponds to poly(vinyl chloride) (PVC) constructed with head–head and tail–tail linkages of the vinyl chloride unit. Benzene, toluene, ethyl‐benzene, o‐xylene, styrene, vinyltoluene, chlorobenzenes, naphthalene, and methylnaphthalenes were detected in the pyrolysis products from CPB above 300°C, and no hydrocarbons could be detected at 200°C. The pyrolysis products from CPB were similar to those from PVC and new products could not be detected. Lower aliphatics, toluene, ethylbenzene, o‐xylene, chlorobenzenes, and methylnaphthalenes were released more easily from pyrolysis of CPB than from PVC; amounts of benzene, styrene, and naphthalene formed were small. These results support the conclusion that recombination of chlorine atoms with the double bonds in the polyene chain takes place and that scission of the main chain may depend on the location of methylene groups isolated along the polyene chain during the thermal decomposition of PVC.
Cationic polymerization of styrene by acetyl perchlorate. II. Steric structure of the polymer and nature of the propagating species
Authors: Higashimura Toshinobu , Kishiro Osamu , Matsuzaki Kei , Uryu Toshiyuki 
Published: April 2003

AbstractCationic polymerization of styrene initiated by acetyl perchlorate in CH2Cl2 yields a polymer having a bimodal molecular weight distribution. The high molecular weight and the low molecular weight portions of the polymer were separated by thin‐layer chromatography, and the steric structure of these separated polymers was investigated by 13C NMR spectra. The high molecular weight polymer had a larger racemic dyad content than the low molecular weight material. From the dependence of the steric structure of the polymer on the polarity of a solvent, it was estimated that the propagating species producing the high molecular weight material was a loose ion pair or a free ion, and that producing the high molecular weight material was a loose ion pair or a free ion, and that producing the low one was a nondissociated species.
Influence of six‐ and eight‐membered rings on the dynamical behavior of polymers
Authors: Kotlík P. , Heidingsfeld V. , Zelinger J. 
Published: April 2003

AbstractDynamic‐mechanical properties of mixtures of polymers with low molecular weight substances containing six‐ and eight‐membered rings were studied. Secondary relaxations have been found and interpreted by means of the theory of conformational motions. There is good agreement of the results with literature data.
Terpolymerization studies. III. Terpolymerization of acrylonitrile, styrene, and α‐cyanocinnamamide
Authors: Liebersohn Aharon , Kohn David H. 
Published: April 2003

AbstractAcrylonitrile (M1), styrene (M2), and α‐cyanocinnamamide (α‐CCA) (M3) were terpolymerized by thermal initiation to low conversion, and the monomer feed/terpolymer composition relationship was determined by Slocombe's triangular graph. The solubility, the thermal behavior, the impact strength, and the chemical resistance of the terpolymers of various compositions were investigated.
Outer‐sphere electron‐transfer reactions of co(III)–polymer complexes in relation to its polymer effects
Authors: Tsuchida Eishun , Shigehara Kiyotaka , Kurimura Yoshimi 
Published: April 2003

AbstractThe outer‐sphere electron‐transfer reactions between [Co(III)(NH3)5L] (CIO4)3 [L = polyethyleneimine (PEI), L = NH3(Amm)] or cis‐[Co(III)(en)2L′Cl]Cl2 [L′ = poly‐N‐vinyl‐2‐methylimidazole(PVI), poly‐4‐vinylpyridine (PVP), N‐ethylimidazole (NEI), pyridine (Py)] and various Fe(II) were studied. In the reaction with Fe(II)‐(phen)32+, the reactivity of Co(III)–PEI was smaller than that of Co(III)–Amm due to the larger electrostatic repulsion. On the other hand, the reactivity of Co(III)–PEI was larger by a factor of 80 in the reaction with Fe(II)(H2O)62+. From the results of rapid‐scanning spectroscopy, the higher reactivity of Co(III)–PEI is caused by the coordination of free ethyleneimine residues in the Co(III)–PEI to Fe(II)–ion. Further more, the hydrophobic interaction between heteroaromatic polymer ligands and Fe(II)‐(phen)32+ brought about the higher reactivities of Co(III)–PVI and Co(III)–PVP. Three interactions caused by the essential properties of polymers are discussed in relation to conformational changes.
Effect of metals on melt oxidation of polyethylene
Authors: Egorenkov N. I. , Lin D. G. , Bely V. A. 
Published: April 2003

AbstractOxidation of polyethylene (PE) melts in contact with metals (Cu, Pb, Au, Al, Zn, Ag) has been studied by infrared spectroscopy and differential thermal analysis (DTA). These metals may be divided into two groups, depending on their activity for oxidizing PE: namely, high‐activity metals (Cu, Pb, Ag, Zn) and low‐activity metals (Al, Au). During the oxidation of PE in contact with high‐activity metals dissolution of the surface layer of metal is observed with accumulation of metal‐containing compounds (salts of carboxylic acids) in the bulk of the polymer. With low‐activity metals these phenomena are not observed. The rate of oxidation of PE on low‐activity metals approaches the oxidation rate of nonmetals (polytetrafluoroethylene and inorganic glass). With certain high‐activity metals (Cu, Pb) the process of oxidation is accelerated only in the early stage of oxidation; then the oxidation rate slows down and the oxidation process ceases. PE films separated from metal after being oxidized on it possess chemical memory, i.e., their oxidation rate depends on the nature of the metal with which they had been in contact, and on the duration of the contact oxidation. The effect of salts of carboxylic acids (metal stearates) on the oxidation of PE melts was also studied. Based on the data obtained, it is concluded that the rate of oxidation of PE melts on high‐activity metals is controlled by metal‐containing compounds which are the products of contact reactions.
Photopolymerization of methyl methacrylate and some other vinyl monomers with the use of chlorine as photoinitiator
Authors: Ghosh Premamoy , Chakraborty Soumen 
Published: April 2003

AbstractLow concentrations (0.001–0.03M) of chlorine easily induce photopolymerization of MMA at 40°C. Kinetic data indicate that polymerization follows a radical mechanism involving complexation of monomer by the initiator and initiation takes place through radical generation during photodecomposition of the initiator‐monomer complex. Termination appears to take place bimolecularly. The kp2/kt value for MMA polymerization at 40°C was found to be 0.83 × 10−2. Rates of chlorine‐initiated photopolymerization were found to decrease in the order MMA, EMA ≫ VA, Sty > MA.
Pyrolysis and gas chromatography of plasma‐polymerized ethylene
Authors: Seeger Michael , Barrall Edward M. , Shen Mitchel 
Published: April 2003

AbstractPlasma‐polymerized polyethylene (PPE) obtained on a radio‐frequency glow discharge has been analyzed by flash pyrolysis combined with in‐line hydrogenation and gas chromatography. The pyrogram of a bulk powder PPE, which had been characterized by both infrared spectroscopy and density measurements, was compared with a 400 Å thick PPE film deposited directly on the pyrolysis probe. Although the two pyrograms have a qualitative resemblance, they are substantially different from that of conventional branched polyethylene (PE). Some of the fragments exhibited by the deposited PPE are also present in pyrograms of 1,4‐polybutadiene. It is evident that the deposited film is a highly branched and unsaturated network polymer with a random arrangement of these structural features.
Reactive polypeptides. II. Photochemistry of poly(γ‐cinnamyl L‐glutamate)
Authors: Kadoma Yoshinori , Ueno Akihiko , Takeda Kenji , Uno Keikichi , Iwakura Yoshio 
Published: April 2003

AbstractPoly(γ‐cinnamyl L‐glutamate) was irradiated in the presence and absence of benzophenone in dichloroethane. The irradiated polymers were analyzed by gas chromatography after hydrolysis. It was possible to assign the transformation in the presence of benzophenone to trans‐cis photoisomerization by comparing the effects with those observed for a model compound cinnamyl acetate. The equilibrium composition of cis and trans isomers in the photostationary state was similar for the model compound and the polypeptide. Photoisomerization was found to be accompanied by marked side reactions for the direct irradiation. Circular dichroism spectra were empolyed to study the structure, and no changes in the structure were found for the irradiated polymers.
Photoinitiation by radical‐cationic mechanism in the polymerization of isobutylene with lewis acids
Authors: Marek M. , Toman L. , Pilař J. 
Published: April 2003

AbstractESR spectra of Lewis acids (VCl4, TiCl4, TiBr4, SnCl4, and AlBr3) and their mixtures with isobutylene were investigated in a n‐heptane solution in the dark and under irradiation at 400–480 nm at −80 to −150°C. A signal was observed only upon irradiating mixtures of VCl4, TiCl4, or TiBr4 and isobutylene. The signal was identified as an isobutylene radical‐cation by comparison with a simulated spectrum. A signal indicating the presence of peroxy radicals were recorded in measurements carried out in the presence of oxygen; these radicals originated from reaction of the isobutylene radical‐cation with oxygen. Radical‐cation initiation by visible light is indicated by the polymerization of isobutylene by VCl4, TiCl4, and TiBr4 and by ESR spectra. The inhibiting effect of oxygen in photochemically initiated polymerization of isobutylene was also elucidated.
Chromatographic techniques for rapid measurement of gel in elastomers
Authors: Gaylor V. F. , James H. L. , Herdering J. P. 
Published: April 2003

AbstractTechniques for measuring gel contents of elastomers by liquid exclusion chromatography are described. Chromatographic methods are based on solubilizing aqueous latex in a water‐miscible elastomer solvent. The resulting mixture of solubilized elastomer and dispersed gel particles is separated and analyzed by liquid chromatography, columns packed with porous glass particles and a differential refractometer detector being used. Applicability of these techniques is illustrated with results for typical nitrile elastomers in methyl ethyl ketone. Chromatographically measured gel contents in the range 30–80% gel were in good agreement with those measured by a classical, 3‐day static method. Repeatability of chromatographic measurement was ±1.35% gel. The entire analysis, including solution preparation, required less than 1 hr and can be as short as 10–20 min.
Ethylene polymerization studies with supported cyclopentadienyl, arene, and allyl chromium catalysts
Authors: Karol Frederick J. , Johnson Robert N. 
Published: April 2003

AbstractHighly active catalysts for low pressure ethylene polymerization are formed when chromocene, bis (benzene)‐ or bis (cumene)‐chromium or tris‐ or bis (allyl)‐chromium compounds are deposited on high surface area silica‐alumina or silica supports. Each catalyst type shows its own unique behavior in preparation, polymerization, activity, isomerization, and response to hydrogen as a chain transfer agent. The arene chromium compounds require an acidic support (silicaalumina) or thermal aging with silica to form a highly active catalyst. At 90°C polymerization temperature arene chromium catalysts produced high molecular weight polyethylene and showed, in contrast to supported chromocene catalysts, a much lower response to hydrogen as a chain transfer agent. An increase in polymerization temperature caused a significant decrease in polymer molecular weight. Addition of cyclopentadiene to supported bis (cumene)‐chromium catalyst led to a new catalyst which showed a chain transfer response to hydrogen typical of a supported chromocene catalyst. Polymerization activity with tris‐ or bis (allyl)‐chromium appears to depend on the divalent chromium content in the catalyst. Changes in the silica dehydration temperature of supported allyl chromium catalyst have a significant effect on the resulting polymer molecular weight. High molecular weight polymers were formed with catalysts that were prepared using silica dehydration temperatures below about 400°C. Dimers, trimers, and oligomers of ethylene were usually formed with catalysts that were prepared on silica dehydrated much above 400°C. The order of activity of the different types of catalysts was chromocene/silica > chromocene/silica‐alumina > bis (arene)‐chromium/silica‐alumina ≃ allyl chromium/silica.