bluuebunny/crossref_metadata_2025_split huggingface dataset:
New processable polyaromatic esters curable by intramolecular cyclization. XVIII
Authors: Chen Paul Y. , Marvel C. S. 
Published: April 2003

AbstractNew processable polyaromatic esters were prepared from 2,2′‐diiododiphenyl‐4,4′‐dicarbonyl dichloride (I), isophthaloyl chloride (II), and/or terephthaloyl chloride (III) with 4,4′‐isopropylidene diphenol (IV), 4,4′‐sulfonyldiphenol (V), or resorcinol by interfacial condensation. In these polymers phenylacetylenyl groups were introduced by replacing the iodine. This process led to soluble and curable polymers. Polymer films can be prepared. After curing the polymers were insoluble and showed excellent thermal and chemical resistance. The curing process increased the polymers' softening temperature about 20°C.
The mechanism of the high‐pressure free radical polymerization of ethylene
Authors: Stoiljkovich D. , Jovanovićch S. 
Published: April 2003

AbstractThe reaction path of the free radical polymerization of ethylene is usually considered identical to the polymerization mechanism of other vinyl monomers. Available experimental data on the polymerization of ethylene, however, hardly fitted the well‐established path of free radical polymerization. Obviously the mechanism of ethylene polymerization is more complex and not well understood. One reason for this, in our opinion, is insufficient knowledge of the physicochemical state of ethylene under high pressure. A model that described the behavior of ethylene under compression has been proposed. According to the model, and increase in pressure causes the formation of various supermolecular forms of ethylene, each accompanied by transition of the second order. By proposing a stereochemical shape for each supermolecular form calculation of activation volumes for each of these transitions was made. Good agreement was obtained when calculated volumes of activation were compared with corresponding experimental values in the literature.
Polymerization of chlorophenyl glycidyl ethers. VIII. Initiation of the polymerization of p‐chlorophenyl glycidyl ether and phenyl glycidyl ether by the system aluminum isopropoxide and zinc chloride (1:1)
Authors: Jedliński Z. , Bero M. , Szewczyk P. , Dworak A. 
Published: April 2003

AbstractLabeled aluminum alcoholate was used to determine the content of end groups of polyethers formed in polymerization reactions initiated by the system Al(OiPr)3 + ZnCl2 (1:1). The polymerization process proceeded in several successive stages. Polymerization initiation and propagation mechanisms were proposed.
Spontaneous copolymerization of 1,3‐cyclohexadiene with polar vinyl monomers
Authors: Nagai Katsutoshi , Machida Shuji , Nonaka Toshiaki 
Published: April 2003

AbstractIn the reactions of 1,3‐cyclohexadiene(1,3‐CHD) with polar vinyl monomers, CH2C(X)Y (X is ‐CN and CO2CH3; Y is CI, H, and CH3), the two α‐chlorosubstituted monomers underwent rapid spontaneous copolymerization, accompanied by the formation of a small amount of cycloadduct. Both polar monomers also gave predominantly copolymers in the reaction with 1,3‐cycloheptadiene(1,3‐CHpD) in lower yield. 1,3‐Cyclooctadiene (1,3‐COD) reacted only with α‐chloroacrylonitrile (CAN) to give a copolymer, while only cycloaddition took place in systems involving cyclopentadiene(CPD) as diene. The charge–transfer (CT) complex formation of 1,3‐CHD with CAN and methyl α‐chloroacrylate(MCA) was confirmed by ultraviolet spectroscopic studies and the equilibrium constants estimated were 0.18 and 0.07 liter/mole, respectively, at 25°C in chloroform as solvent. The activation energies for the copolymerizations of 1,3‐CHD with CAN and MCA in benzene were determined to be ca. 6.6 and 9.6 kcal/mole, respectively. In the system composed of 1,3‐CHD and CAN, only the copolymerization was affected by solvents used and oxygen. Although addition of ZnCl2 to the system resulted in the acceleration of the both reactions, the variation in the product ratio of copolymer to cycloadduct with ZnCl2 concentration showed a maximum. Based on the results in the present and preceding studies for systems involving 1,3‐cyclodienes and acceptor monomers, the relationship between the cycloaddition and the spontaneous copolymerization is discussed.
Preparation of macroreticular redox resins with hydroquinone and catechol units as pendant groups and their properties
Authors: Iwabuchi Susumu , Nakahira Takayuki , Fukushima Yoshitaka , Saito Osamu , Kojima Kuniharu 
Published: April 2003

AbstractMacroreticular redox resins with hydroquinone and catechol units as pendant groups were prepared by the Friedel‐Crafts reaction of macroreticular styrene/divinylbenzene copolymer with 2,5‐ and 3,4‐dimethoxybenzyl chlorides, followed by removal of the methyl groups with hydrobromic acid. The redox capacity of the macroreticular resins was determined by oxidation of hydrazobenzene with resins in oxidized form. Resins with 1,4‐benzoquinone units were capable of oxidizing hydrazobenzene, whereas those with 1,2‐benzoquinone (catechol quinone) units exhibited no apparent oxidative ability; this seems to be due to a complex formation between azobenzene and the catechol units in the reduced resins. Adsorption of metallic ions onto catechol‐containing resins showed a high selectivity for Hg2+ ion. The effects of pH, reaction time, and ion concentration on the adsorption were also studied.
Formation of polymer‐bonded nitroxyl radicals in the UV stabilization of polypropylene by a bifunctional hindered amine light stabilizer
Authors: Hodgeman Daryl K. C. 
Published: April 2003

AbstractThe formation of polymer‐bonded stabilizer derivatives during photooxidation of isotactic polypropylene, which contains the hindered amine light stabilizer bis(2,2,6,6‐tetramethyl‐4‐piperidinyl) sebacate and the corresponding bisnitroxyl radical, was investigated. The photooxidized polypropylene films that contain these additives were studied by ESR, IR, and nitrogen analysis before and after exhaustive solvent extraction of the photooxidized films. ESR showed that under the conditions in use a maximum of 20% of the nitroxyl radicals formed from the hindered amine was bonded to the polymer chain. Regeneration of nitroxyl radicals from the polymer‐bonded stabilizer derivatives under photooxidative conditions indicated that the stabilizer was bonded to the polymer chain by O‐alkyl‐substituted hydroxylamine linkages >NOPP.
Catalyzed chain transfer to monomer in free radical polymerization
Authors: Enikolopyan N. S. , Smirnov B. R. , Ponomarev G. V. , Belgovskii I. M. 
Published: April 2003

AbstractThe kinetics and the molecular weight distribution in the radical polymerization of methyl methacrylate in the presence of a cobalt complex of hematoporphyrin tetramethyl ether is investigated. The whole complex of experimental data indicates the new kinetic phenomenon—catalyzed chain transfer to monomer. The possible mechanism of the chain transfer and the chain transfer agent regeneration acts is suggested.
Hyperfine structure observed in EPR spectra of polyphenylacetylene solutions
Authors: Whitte W. M. , Kang E. T. , Ehrlich P. , Carroll J. B. , Allendoerfer R. D. 
Published: April 2003

AbstractThe high‐temperature (>120C) electron paramagnetic resonance (EPR) spectrum of solutions of polyphenylacetylene have been deconvoluted into the spectra of two separate radicals, a delocalized π radical, whose EPR spectrum consists of a single 15‐G wide Gaussian line comprising about 90% of the total signal and a second, more localized π radical exhibiting complex hyperfine structure in its EPR spectrum. Some possible structures for the minor component radical are suggested and their hyperfine splitting constants calculated using molecular orbital theory.
Thermal rearrangements of polybutadienes with different vinyl contents
Authors: Golub Morton A. 
Published: April 2003

AbstractA study was made of the loss of double bonds in equibinary (1,4‐1,2) polybutadiene (EB) and in polybutadienes with 30% 1,2, 70% 1,4 (FI), and 10% 1,2, 90% 1,4 (DI) double‐bond content, when heated in vacuum under nonpyrolytic conditions (temperature range 220–280°C). These polymers were found to undergo second‐order loss of 1,2 unsaturation with similar activation energies (Ea = 34.0 ± 3 kcal/mole), by analogy to the previously reported thermally induced loss of double bonds in 1,2‐polybutadiene (VB) (Ea = 33.6 ± 3 kcal/mole). Moreover, EB and FI exhibited also second‐order loss of 1,4 unsaturation, with Ea ca. 36 and 40 kcal/mole, respectively, while DI showed negligible loss of 1,4 unsaturation below 260°C, in common with cis‐1,4‐polybutadiene (CB) (with 2% 1,2 double bonds) examined earlier. The loss of 1,2 double bonds in the various polybutadienes with different vinyl contents is accompanied by substantial methyl production, ranging from about one methyl group formed for every 4–5 vinyl units lost in VB, to one methyl for every two vinyls lost in EB, and to almost one methyl for each vinyl lost in DI or CB. Mechanisms are proposed for the thermally induced loss of 1,2 and 1,4 unsaturation in various polybutadienes and for the accompanying methyl production.
Irradiation of aromatic polymers: The effect of irradiation temperature on crosslinking and scission in polystyrene
Authors: Bowmer Trevor N. , O'Donnell James H. , Winzor Donald J. 
Published: April 2003

AbstractPolystyrene of narrow molecular weight distribution, Mw/Mn ≈ 1.03, was subjected to γ irradiation at 100 and 150°C. The yields of scission and crosslinking, G(S) and G(X), where determined from the changes in molecular weight distribution using gel permeation chromatography, (GPC) with supporting evidence from osmometry and viscometry. The ratio G(S)/G(X) increased from 0.02 at 30°C, obtained previously, to 2.8 at 150°C. This was mainly due to a tenfold increase in G(S), whereas G(X) apparently decreased slightly. These results are compatible with increased disproportion of chain scission radicals relative to their combination, analogous to the temperature dependence of mutual termination in the free radical polymerization of styrene. There was no obvious discontinuity through the glass transition temperature, although there may be a change in sign of the temperature coefficient of G(X). This system provides an excellent example of the applicability of measurements of molecular weight distributions and averages to determinations of G(S) and G(X) under conditions when gel measurements are inappropriate, either because of the failure of the system to form gel, or, as in the present case, because of the very large radiation doses required for gel formation.
Studies of redox polymerization. I. Aqueous polymerization of acrylamide by an ascorbic acid–peroxydisulfate system
Authors: Narain H. , Jagadale S. M. , Ghatge N. D. 
Published: April 2003

AbstractThe polymerization of acrylamide initiated by an ascorbic acid–peroxydisulfate redox system was studied in aqueous solution at 35 ± 0.2°C in the presence of air. The concentrations studied were [monomer] = (2.0–15.0) × 10−2 mole/liter; [peroxydisulfate] = (1.5–10.0) × 10−3 mole/liter; and [ascorbic acid] = (2.84–28.4) × 10−4 mole/liter; temperatures were between 25–50°C. Within these ranges the initial rate showed a half‐order dependence on peroxydisulfate, a first‐order dependence on an initial monomer concentration, and a first‐order dependence on a low concentration of ascorbic acid [(2.84–8.54) × 10−4 mole/liter]. At higher concentrations of ascorbic acid the rate remained constant in the concentration range (8.54–22.72) × 10−4 mole/liter, then varied as an inverse halfpower at still higher concentrations of ascorbic acid [(22.72–28.4) × 10−4 mole/liter]. The initial rate increased with an increase in polymerization temperature. The overall energy of activation was 12.203 kcal/mole in a temperature range of 25–50°C. Water‐miscible organic solvents depressed the initial rate and the limiting conversion. The viscometric average molecular weight increased with an increase in temperature and initial monomer concentration but decreased with increasing concentration of peroxydisulfate and an additive, dimethyl formamide (DMF).
Preparation and thermal behavior of poly‐p‐phenylene diacrylic acid dimethyl ester
Authors: Hasegawa Masaki , Yurugi Tadashi , Namiki Satoru , Shiobara Takatoshi , Nakanishi Hachiro , Nakanishi Fusae 
Published: April 2003

AbstractThe photopolymerization behavior of p‐phenylene diacrylic acid dimethyl ester (p‐PDA Me) crystal and the thermal behavior of the resultant poly‐p‐PDA Me were investigated. From the kinetic study of polymerization at various temperatures a topochemical process via a stepwise mechanism was observed. Continuous change from monomer to polymer crystals was demonstrated by x‐ray diffraction pattern and DSC analysis. Crystallinity of the reacting phase was maintained at an extremely high degree during the polymerization process in support of monomer crystal lattice control. Thermal study on as‐polymerized poly‐p‐PDA Me crystal confirmed that the thermal reaction was a polymer crystal lattice‐controlled depolymerization, which was followed by miscellaneous processes that involved vaporization, sublimation, and deterioration of the oligomeric or monomeric units of p‐PDA Me. Thermal stability was dependent on the molecular weight. All the results are compared with those of four‐center‐type photopolymerization in the crystalline state.
Redox polymerization‐kinetics of the reaction inititated by the system CH2(CH)2MN(III) in aqueous H2SO4 and the system CH2(CN)2MN(OAC)3 in DMF and acetic acid
Authors: Jayakrishnan Athipettah , Haragopal Mahadevan , Mahadevan Venkatanarayana 
Published: April 2003

AbstractPolymerization of acrylonitrile and methyl methacrylate by the redox systems propanedinitrile‐Mn(III) in aqueous sulfuric acid and propanedinitrile‐Mn(OAc)3 in DMF and glacial acetic acid was investigated in the temperature range 20–40°C. The kinetics are consistent with the formation of an intermediate complex whose irreversible decomposition yields the initiating radical. With both monomers mutual termination predominates. The main difference between aqueous H2SO4 and acetic acid compared with DMF lies in the ease of oxidation of the primary radicals by the oxidant. Rate and equilibrium parameters were estimated and their significance discussed.
The preparation and reactions of polymeric azides. I. The reaction of poly(vinylbenzyl azide) with acetylenic and olefinic derivatives
Authors: Cohen H. L. 
Published: April 2003

AbstractThe preparation and reactions of polymers and copolymers of vinylbenzyl azide with olefinic and acetylenic derivatives are described. With acetylenes, a 1,3‐dipolar addition gave almost complete conversion to polymeric 1,2,3‐triazoles. Yields were excellent and light‐colored derivatives were obtained.
Charge transfer polycondensation of diethyl chelidonate with diamines in the presence of polyvinylcarbazole
Authors: Ogata Naoya , Sanui Kohei , Abe Masahiko 
Published: April 2003

AbstractPolycondensation of diethyl chelidonate (DEC), which contains an electron‐accepting γ‐pyrone nucleus, with hexamethylenediamine (HMD) takes place easily even at room temperature to form a corresponding polyamide. Since DEC was expected to form a charge transfer complex with an electron‐donating compound such as polyvinylcarbazole (PVK), the polycondensation of DEC with diamines was carried out in the presence of PVK as a matrix. It was found that the rate of the polycondensation of DEC with diamines in dioxane was enhanced either by the presence of PVK or by the irradiation with ultraviolet (UV) light. Moreover, the polycondensation of DEC with HMD in the presence of PVK was accelerated by the UV irradiation, probably owing to the transfer of light energy.
Gamma radiation‐initiated polymerization of styrene at high pressure. II. Chain termination
Authors: Moore P. W. , Clouston J. G. , Chaplin R. P. 
Published: April 2003

AbstractThe pressure dependence of the termination rate constant kt for the free radical polymerization of monomers such as styrene is a function of polymer chain length, chain stiffness, and monomer viscosity, all of which influence the rate of segmental diffusion of an active radical chain end out of the coiled polymer chain to a position in which it can react with a proximate radical. Although kt is not sensitive to changes in chain length, the large increase in molecular weight is responsible for a significant reduction in kt at high pressures. For most of the common vinyl polymers, which exhibit some degree of chain stiffness, kt is inversely proportional to a fractional power of the monomer viscosity because it depends in part on the resistance of chain segments to movement and in part on the influence of viscosity in controlling diffusion of the chain ends. The fractional exponent appears to increase with pressure and this is interpreted as evidence that the polymer chains become more flexible in a more viscous solvent. Because the fractional exponent is higher for more flexible chains, the value of the activation volume for chain termination is an indication of the degree of flexibility of the polymer chains, provided that the monomer is a good solvent for the polymer and that chain transfer is negligible.
Mechanisms of thermal decomposition in totally aromatic polyurethanes
Authors: Foti S. , Maravigna P. , Montaudo G. 
Published: April 2003

AbstractThe primary fragmentation mechanisms in the thermal decomposition of polyurethanes were studied in detail by direct pyrolysis into the mass spectrometer. The remarkable difference in the thermal stability of the two totally aromatic polyurethanes I and II (Fig. 1) reflects their different decomposition pathways. In fact, polymer I undergoes a depolycondensation process that yields diiscyanate and dialcohol as primary thermal fragments. The thermal decomposition of polymer II proceeds instead via the formation of a cyclic compound that has been isolated and characterized. In contrast, open‐chain fragments are generated in the thermal decomposition of the partially aliphatic polymer III.
Kinetic approach to radiation‐induced grafting in the polyethylene‐styrene system. IV. Comparison between high density polyethylene and low density polyethylene
Authors: Imai Masahiko 
Published: April 2003

AbstractThe investigation method reported in earlier articles was applied to preirradiation methods of the reaction of low‐density polyethylene (LDPE) in liquid and vapor and compared with high‐density polyethylene (HDPE). Monomer concentrations during reactions and monomer feed rates were determined gravimetrically. Increasing patterns of the degree of grafting were obtained and compared. Monomer concentration during the reactions was lower in LDPE than HDPE and radical decay was more rapid in LDPE. A model calculation was applied to this experiment and a schematic explanation was attempted. The differences between the reaction mechanisms of HDPE and LDPE are explained.
Effects of water, methanol, and ethanol on the production of starch‐g‐polystyrene copolymers by cobalt‐60 irradiation
Authors: Henderson Alex M. , Rudin Alfred 
Published: April 2003

AbstractStarch‐g‐polystyrene copolymers were made by simultaneous 60Co irradiation of mixtures of wheat starch and styrene at room temperature. The extent of conversion of monomer to polymer is increased drastically with increasing water content up to a level of about 26 wt % on starch. Methanol had approximately the same effect as water at equivalent concentrations but ethanol was clearly less effective as a promoter of homo‐ and graft copolymerizations. Drying the starch reduced the conversion to polymer with all promoters but caused the greatest deterioration in the ability of ethanol to promote polymerization. The effects of physically swelling the starch by freeze drying the gelatinized material were also studied, as were preirradiation graft copolymerizations. The effects of promoters on graft polymerization parallel their abilities to scavenge stable radicals in irradiated starch. Water and methanol are better radical scavengers and polymerization promoters because they are better able to disrupt hydrogen bonds and permeate the starch structure. Radiolysis of the promoter is important in the grafting reaction.
Effect of carbon on sulfuration under a binary accelerator system
Authors: Das C. K. , Fegade N. B. , Millns W. 
Published: April 2003

AbstractThe continuous measurements of cure characteristics were monitored with a Monsanto rheometer and compared with the volume swell measurement of cross‐link density in benzene. Both methods of measurement indicated the formation of a complex of MBT and DPG in equimolar proportions, confirmed by the chemical probe technique and activation energy data. Presence of HAF did not alter vulcanization; that is, HAF has almost no qualitative effect on the kinetics of sulfuration but some on the state of the cure, optimum cure time, and onset and rate of vulcanization. Activation energy remained unchanged by the addition of HAF black.
Interaction between dyes and polyelectrolytes. XII. Excitation energy transfer between bound dyes
Authors: Shirai Masamitsu , Ohyabu Motoshi , Tanaka Makoto 
Published: April 2003

AbstractMethylene blue‐photosensitized isomerization of cis‐p‐(phenylazo) phenyltrimethylammonium iodide to the transisomer was used advantageously to investigate the effect of polyanions on the triplet excitation energy trasfer between cationic dyes in aqueous media. The efficiency of the excitation energy transfer was improved by the addition of potassium poly(vinyl sulfate) (PVS), potassium poly(styrene‐sulfonate) (PSS), sodium poly(acrylate) (PAA), and sodium poly(methacrylate) (PMA) and was dependent on the polyanion concentration in the system. PVS and PSS were much more effective than PAA and PMA. The efficiency of the excitation energy transfer under the most appropriate conditions was about 67 times higher than in the absence of polyanions. Correlation with dye binding to polyanions and the efficiency of the excitation energy transfer between dyes was discussed.
Preparation of copoly(vinyl alcohol‐styrenesulfonic acid) resin and its catalytic activity on hydrolysis of carbohydrates. III. Kinetic analysis of the catalysis
Authors: Arai Kenichiro , Ogiwara Yoshitaka , Kuwabara Chiharu 
Published: April 2003

AbstractHydrolysis of dextrin in the presence of copoly(vinyl alcohol‐styrenesulfonic acid) resin was investigated kinetically. The hydrolysis rate increased nearly proportionally with increases in the concentrations of the substrate and the catalyst copolymer. This is in contrast to the results found in a similar homogeneous reaction in the presence of soluble copoly(vinyl alcohol–styrenesulfonic acid) in which the reaction rate clearly followed Michaelis–Menten type kinetics. However, the hydrolysis was inhibited by the addition of copoly(vinyl alcohol–styrene) resin or poly(vinyl alcohol). Activation parameters of the hydrolysis in the presence of the copolymer resin as catalyst were also investigated, and it was found that the enthalpy and entropy of the activation in the presence of the copolymer resin were lower than those in Amberlite 120B and slightly decreased when vinyl alcohol unit was introduced. From these results it was concluded that the poly(vinyl alcohol) sequence introduced into the insoluble catalyst copolymer resin also played an important part in the acceleration of dextrin hydrolysis in a manner similar to the case of a soluble catalyst, although the interaction with the substrate was weaker.