bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐conversion polymerization. I. Theory and application to methyl methacrylate
Authors: Cardenas J. N. , O'Driscoll K. F. 
Published: April 2003

AbstractThe concept of polymer entanglements has been applied in conjunction with classical free‐radical kinetics to describe vinyl polymerizations carried to high conversion. A kinetic model has been developed on the assumption that two populations of radicals exist in a high‐conversion polymerization system: those radicals whose chain lengths are long enough to become entangled with neighboring molecules and have, therefore, a restricted mobility; and those shorter radicals whose mobilities are not strongly affected by diffusional effects. It has also been assumed that the kinetic rate constant for the termination step between entangled radicals is inversely proportional to the mean entanglement density. The model contains only two parameters in addition to the kinetic rate constants required to describe low‐conversion polymerizations. One of these parameters can be determined, at least in principle, from measurements of solution properties of the polymer‐monomer mixtures. The model so developed has been tested against experimental data obtained from the literature on the bulk polymerization of methyl methacrylate. The agreement between predicted and experimental monomer conversions and molecular weight averages is found to be satisfactory.
Polymerization of pyridazine and pyridazinone derivatives. XIV. Effects of solvent, concentration, and temperature on radical copolymerizability of 3(2‐methyl)6‐methylpyridazinone with styrene
Authors: Matsubara Yoshio , Yoshihara Masakuni , Maeshima Toshihisa 
Published: April 2003

AbstractThe free‐radical copolymerizability of 3(2‐methyl)6‐methylpyridazinone (I) with styrene (St)(M1) has been reinvestigated at varying reaction conditions (solvent, monomer concentration, and reaction temperature). The copolymerization rates in protic solvents were not proportional to the monomer concentration. The overall activation energies in protic solvents were much affected by the monomer concentration. The results might be ascribed to the viscosity effect on the termination reaction, because the protic solvent was found to interact with I through hydrogen bonding to form a 1:1 complex which changed the viscosity of the reaction mixture. The monomer reactivity ratios were strongly affected by the reaction conditions. This might be explained by taking account of the solvation to the carbonyl group of I in the transition state, because clear relationships were not obtained by plots of log 1/r1 against the values of both vCO and vCC stretching frequencies of I, but the values of both ΔΔH‡(ΔH‡11 − ΔH‡12) and ΔΔS‡(ΔS‡11 − ΔS‡12) decreased linearly with a decrease of the monomer concentration in order of benzene ∼ dimethylformamide < ethanol < phenol < acetic acid systems.
Role of polymer ligands in the oxygenation of metal chlorophyllins
Authors: Tsuchida Eishun , Shigehara Kiyotaka , Miyamoto Ken 
Published: April 2003

AbstractIn order to obtain information about the characteristics of polymer‐(metal chlorophyllins), their redox and oxygenation reactions were studied. Complexes composed of metal chlorophyllins (MChn) and partially quaternized poly(4‐vinylpyridine) (QPVP) exhibited an increased stability due to electrostatic interaction between polymer cation and carboxylate anions of side groups in the MChn. The reduction of these polymer complexes by S2O42‐ occurred easily with an decrease in their apparent reduction potentials. The resulting low‐valence complexes had an ability to absorb molecular oxygen. The oxygenation of these polymer complexes was not completely reversible; however the rate of the irreversible reoxidation was less by a factor of 1010 for the polymeric complex than that for the monomeric MChn‐pyridine complex. The stability of these oxygen complexes is discussed in relation to the hydrophobicity of QPVPs.
Interaction of poly(vinylpyrrolidone) with methyl orange and its homologs in aqueous solution over the temperature range 60–90°c
Authors: Takagishi Toru , Nakagami Kimio , Imajo Koichi , Kuroki Nobuhiko 
Published: April 2003

AbstractThe binding of methyl orange, ethyl orange, propyl orange, and butyl orange by poly(vinylpyrrolidone) has been examined by a technique of equilibrium dialysis over a high temperature range (60–90°C). The first binding constants and the thermodynamic parameters in the course of the binding were evaluated. The results obtained at these temperatures were compared to those at lower ones (5–35°C) described previously in order to estimate the contribution of hydrophobic bonds to the binding. It was found that at the 60–90°C range complex formation between the dye and the macromolecule is associated with an exothermic enthalpy change and a positive entropy change. The enthalpy and entropy changes of the binding are of the order of −4.5 kcal/mole and 6 eu, respectively, for each dye measured. Thus the binding is mainly enthalpy‐controlled. Furthermore the effect of the alkyl chain length of the dye on both the ΔH° and ΔS° values is not pronounced. Also temperature dependences of the ΔH° and ΔS° terms were not observed. All these observations in the higher temperature range can be explained as a result of the disruption of water structure in the binding environment and hence a decrease in hydrophobic bond formation between the dye and the polymer.
Graft copolymerization of styrene on rubber containing halogen by chromous acetate
Authors: Lee Munam , Nakamura Hironobu , Minoura Yuji 
Published: April 2003

AbstractGraft copolymerization of styrene on rubber containing chlorine, e.g., chloroprene rubber (CR) and chlorosulfonated polyethylene (Hypalon), with chromous acetate (Cr2+) was carried out in DMF–THF mixed solvent at 50°C. From the kinetic study, the normal kinetic orders with respect to the concentration of initiator and monomer were obtained at low concentrations of CR, but the deviation from conventional first‐order to second‐order kinetics with respect to the monomer concentration was observed at high CR concentrations: Rp ∝ [CR]1/2 [Cr2+]1/2[styrene]1 (at low CR concentration); Rp ∝ [CR]1/2 [Cr2+]1/2[styrene]1 (at high CR concentration). This result was explained in terms of the high viscosity of the reaction medium due to the rubber contained in solution. An initiation site along the polymer chain was assumed from the graft copolymerization with three kinds of CR having different microstructures. The results of fractionation of obtained polymer showed that the graft efficiency was high but a large amount of gel was formed.
Photopolymerization of methyl methacrylate and some other vinyl monomers with the use of a pyridine–bromine charge‐transfer complex as photoinitiator
Authors: Ghosh Premamoy , Mitra Partha Sarathi 
Published: April 2003

AbstractPolymerization of MMA was carried out under visible light (440 nm) with the use of pyridine–bromine (Py–Br2) charge‐transfer (CT) complex as the photoinitiator. Initiator exponent and intensity exponent were 0.5 and 0.43, respectively, and the monomer exponent was found to be dependent on the nature of the solvent or diluent used. The Polymerization was inhibited in the presence of hydroquinone, but oxygen had very little inhibitory effect. An average value of kp2/kt for this polymerization system was 1.19 × 10−2, and the activation energy of photopolymerization was 4.95 kcal/mole. Kinetic data and other evidence indicate that the overall polymerization takes place by a radical mechanism. With Py–Br2 complex as the photoinitiator, the order of polymerizability at 40°C was found to be MMA, EMA ≫ Sty, MA.
Photopolymerization of methyl methacrylate and other vinyl monomers with the use of N‐bromosuccinimide as photoinitiator
Authors: Ghosh Premamoy , Mitra Partha Sarathi 
Published: April 2003

AbstractPolymerization of MMA was done in the presence of visible light (440 nm) with the use of N‐bromosuccinimide (NBS) as the photoinitiator. The initiator exponent and intensity exponent were 0.5, and the monomer exponent was found to be unity. The polymerization was inhibited in the presence of hydroquinone. The average kp2/kt for this photopolymerization system was found to be 0.296 × 10−2 and the activation energy of photopolymerization was 4.67 kcal/mole. Kinetic and other evidence indicate that the overall polymerization takes place by a radical mechanism. With NBS as the photoinitiator, the order of polymerizability at 40°C was MMA, EMA ≫ MA ≃ VA, and styrene could not be polymerized under similar conditions.
Aspects of plastics scintillators. I. Behavior of fluorescent molecules in polymerizing medium
Authors: Neilson R. D. M. , Soutar I. , Steedman W. 
Published: April 2003

AbstractThe interaction between a number of organic fluors and vinyltoluene during thermally induced polymerization has been investigated by using kinetic and fluorescence techniques. It has been confirmed that 2,5‐diphenyloxazole, bis‐2(5‐phenyloxazoyl)benzene and p‐terphenyl do not react in the polymerizing medium and are present in the final product as solute in a solid solution. However, 1,1′4,4′‐tetraphenyl‐1,3‐butadiene and 9‐methylanthrancene do react, via chain‐transfer steps. The diene is concentrated in the low molecular weight tail of a polymer of broad molecular weight distribution and can be removed by further fractionation. The anthrancene species undergoes structural rearrangement with accompanying loss of fluorescence activity during reaction with the growing polymer chains.
Étude des irregularités observées dans la polymérisation du (−) sulfure de propylene amorcée par le triethylaluminium et ses derivés
Authors: Dumas Philippe , Spassky Nicolas , Sigwalt Pierre 
Published: April 2003

AbstractPolymerization of propylene sulfide by use of triethylaluminum derivatives as initiators leads to low molecular weight polymers with irregularities in the chain, e.g. head‐to‐head units and disulfide bonds. Abnormal chiroptical properties due to the presence of these linkages were observed on polymerizing a levorotatory enantiomer. The formation of irregularities may be explained by the simultaneous presence of anionic and cationic mechanism and gives polymers without irregularities.
Radiation copolymerization of vinylene carbonate with isobutyl vinyl ether
Authors: Schnautz N. G. 
Published: April 2003

AbstractThe radiation‐induced copolymerization of vinylene carbonate (M1) with isobutyl vinyl ether (M2) has been investigated over the temperature range of 40–80°C. The monomer reactivity ratios r1 and r2 were determined to be 0.118 and 0.148, respectively, and an activation energy of 7.6 kcal/mole (31.8 kJ/mole) was calculated for the copolymerization process.
Bimolecular reaction of 2,4,6‐tri‐tert‐butylphenoxyl with hydroperoxide group in a solid polymer matrix
Authors: Griva A. P. , Denisov E. T. 
Published: April 2003

Abstract2,4,6‐Tri‐tert‐butylphenoxyl (TBP) is dissolved and reacted with hydroperoxide groups of polyethylene and polypropylene in the amorphous phase. The reaction is not limited by diffusion, and unlike the case in the liquid phase, the concentration of TBP is not zero at the end of the reaction time, even though hydroperoxide groups are in excess. The biomolecular rate constant is smaller in the solid than it is in the liquid phase and depends on molecular motion. A linear relationship between the rate constant and frequency of rotation of radicals in polymers is observed.
Glass transitions of polyolefins by inverse gas chromatography
Authors: Braun J.‐M. , Guillet J. E. 
Published: April 2003

AbstractThe glass transition temperatures of polypropylene, poly‐1‐butene, polyisobutylene, and an ethylene‐propylene (EP) copolymer have been determined by inverse gas chromatography. The results are consistent with those determined by other procedures. When applied to low‐, medium‐ and high‐density polyethylene, values of −35, −25, and −18°C, respectively, were obtained. Because of the fact that the chromatographic technique involves essentially a sensitive detection of free volume in a polymer, it is suggested that these values represent Tg if it is defined as an iso‐free volume state of the amorphous phase of the polyethylene.
Studies on propagating species in cationic polymerization of styrene derivatives by acetyl perchlorate or iodine. I. Bimodal molecular weight distribution of polymers produced by acetyl perchlorate or iodine
Authors: Higashimura Toshinobu , Kishiro Osamu , Takeda Takashi 
Published: April 2003

AbstractTo investigate the nature of the propagating species in cationic polymerization of para‐substituted styrenes, p‐chlorostyrene (pCIS), p‐methylstyrene (pMS), and p‐methoxystyrene (pMOS), were polymerized with acetyl perchlorate or iodine in various solvents at 0°C, and the molecular weight distribution (MWD) of the polymers was measured by means of gel‐permeation chromatography. When ClO4− was a counterion, poly(pCIS) having a bimodal MWD was produced, while polymers of pMOS and pMS possessed a unimodal MWD, regardless of the solvent polarity. When more nucleophilic I− (or I3−) was a counterion, however, polymers having a bimodal MWD were produced from pMOS and pMS. These results showed that either dissociated or nondissociated propagating species existed in the cationic polymerization of styrene derivatives with acetyl perchlorate or iodine, and that the type of MWD was strongly dependent on the stability of the growing cation and the nucleophilicity of the counterion.
Anionic polymerization of styrene in the presence of pyridine
Authors: Yagi Koji , Tsuyama Shigeo , Toda Fujio , Iwakura Yoshio 
Published: April 2003

AbstractAn interesting effect of pyridine on the anionic polymerization of styrene in THF is described. Pyridine forms a complex with living polystyrene and greatly slows the polymerization rate without changing the degree of polymerization. From kinetic and spectroscopic studies, it was clear that there exist two active species in this system and the complex between living polystyrene and pyridine was of the 1:1 type, which itself had a weak ability to grow. The formation constant of the complex K was found to be about 4 × 105 l./mole. The effect of substituted pyridine was also studied and the nature of the complex was discussed.
Electropolymerization of aminophthalic acids. II. Polymerization of 4‐(4′‐aminobenzamido)‐, 4‐(2′‐aminobenzoyl)‐, and 4‐(3′‐aminobenzoyl) phthalic acid
Authors: Phillips D. Colin , Alvino William M. 
Published: April 2003

AbstractThe electrochemical polymerization of the amino phthalic acid series has been extended to the following derivatives: 4‐(4′‐aminobenzamido), 4‐(2′‐aminobenzoyl), and 4‐(3′‐aminobenzoyl)phthalic acid. Reactions were performed in both dimethylacetamide and ethanol. Both systems produced a film deposit at the anode which was identified as the amide acid of the starting material. Conversion by heat to the imide produced a brittle coating. Inherent viscosity measurements indicate that only low molecular weight material was formed.
Structure and reactivity in cationic polymerization of butadiene derivatives. IV. 1‐alkoxybutadienes
Authors: Otsuki Michihisa , Masuda Toshio , Higashimura Toshinobu 
Published: April 2003

AbstractThe reactivity of trans‐1‐alkoxybutadienes in cationic homopolymerization and copolymerizations and structure of the polymers produced were investigated. 1‐Ethoxybutadiene is polymerized easily at −78°C by various acidic catalysis. The reactivity of 1‐ethoxybutadiene was similar to that of ethyl vinyl ether. The polymers produced possessed molecular weights of several thousands, and were composed of 70–95% 1,4 structure and 5–30% 3,4 structure. In the copolymerization of ethyl vinyl ether (M1) with 1‐ethoxybutadiene at −78°C in toluene by boron trifluoride diethyl etherate, r1 = 1.15, r2 = 2.62. From the Hammett plot of the relative reactivities of alkoxybutadienes (alkoxy: CH3O, C2H5O, i‐C3H7O), the reaction constant p* was determined to be −2.9. Results of the present study were compared with those of various butadiene derivatives.
Morphology of organosilicon ladder polymers
Authors: Andrianov K. A. , Slonimsky G. L. , Zhdanov A. A. , Tsvankin D. Ya. , Levin V. Yu. , Papkov V. S. , Kvachev Yu. P. , Belavtseva E. M. 
Published: April 2003

AbstractThe morphology of organosilicon ladder polymers was studied by various methods, including x‐ray techniques, diffraction of monochromatic polarized light, and electron microscopy. The morphology is discussed as a function of the chemical composition, the molecular weight, and the method of preparation.
Syntheses of polymerizable hydroquinone derivatives
Authors: Kamogawa Hiroyoshi , Kitahora Kunimichi , Hanawa Hidehito , Nanasawa Masato 
Published: April 2003

AbstractSeveral polymerizable hydroquinone derivatives were prepared by the Williamson synthesis. Thus, hydroquinone mono(p‐vinylbenzyl) ether (III‐1), hydroquinone methyl p‐vinylbenzyl ether (III‐4), and hydroquinone benzyl p‐vinylbenzyl ether (III‐5), tert‐butylhydroquinone mono(p‐vinylbenzyl) ether (III‐2), and 2,5‐di‐tert‐butylhydroquinone mono(p‐vinylbenzyl) ether (III‐3) were synthesized by the reactions of p‐chloromethylstyrene with the corresponding hydroquinone derivatives in alcoholic potassium hydroxide or with their potassium salts in dipolar aprotic solvents. All monomers were found to polymerize by free‐radical initiation except III‐3, which required a cationic initiator.
Polycondensation of mono‐ and difunctional derivatives of p‐xylene
Authors: Peppas Nikolaos A. , Valkanas George N. , Diamanti‐Kotsida Eugenia T. 
Published: April 2003

AbstractA new method for the production of polydimethylbenzylenes,$ \rlap{--} [{\rm C}_6 {\rm H}_4 ({\rm CH})_2 {\rm CH}_{\rm 2} \rlap{--} ]_n $, involves the polycondensation of the mono‐ and dichloromethyl and mono‐ and diacetoxymethyl derivatives of p‐xylene via an acid‐catalyzed reaction in anhydrous acetic acid. The reaction of the difunctional derivatives is slower than the reaction of the monofunctional ones, leading to linear, predominantly crystalline, high‐melting polymers with molecular weights of 2000–3000. Polycondensation of both monomers under different feed ratios leads to polymers with the same structure, and the monofunctional monomers condense with themselves more favorably than with the difunctional ones. Thus a head‐to‐head structure is preferred, and crystalline polymers of high structural purity are obtained.
Polymer morphology and random chain scission
Authors: Jellinek H. H. G. 
Published: April 2003

AbstractA theory has been developed for the kinetics of random chain scission of polymers consisting of amorphous and crystalline (spherulite) phases. The degrees of degradation have been derived for such scission due to a gas which in one case is able to penetrate spherulites where degradation is then diffusion‐controlled and in another case cannot diffuse into spherulites. In the later case, special conditions are prevalent in the amorphous–crystalline interface. Main‐chain links in crystalline fold regions are assumed to scission faster than all other main‐chain links due to strain energy.
Short branching in poly(vinyl alcohol). III. Some properties of model polymers of short‐branched poly(vinyl alcohol)
Authors: Morishima Y. , Irie Y. , Iimuro H. , Nozakura S. 
Published: April 2003

AbstractMelting point, the iodine color reaction, and foam fractionation were studied on model poly(vinyl alcohol) (PVA) having short branches of one or two monomer units in length. An increase in the amount of short branching units caused a marked decrease in color intensity of the PVA–iodine reaction and in the melting point. These tendencies were more remarkable when the short branching was two monomer units in length than when it was one monomer unit. It was also found that foam fractionation of an aqueous PVA solution produced PVA fractions with different degree of short branching, the degree increasing with increase in the fraction number. The color intensity of the PVA–iodine reaction has been confirmed to decrease with increase in the fraction number, but this result cannot be explained solely in terms of the short branching. It is concluded that the phenomenon of foam fractionation of PVA and the iodine color reaction of the fraction appear to be governed by many factors such as molecular weight, stereoregularity, and short branching.
Short branching in poly(vinyl alcohol). IV. Determination of the short branches in poly(vinyl alcohol) polymerized under various conditions
Authors: Morishima Y. , Nozakura S. 
Published: April 2003

AbstractThe effect of the conditions of polymerization of vinyl acetate on the formation of short branching in the derived poly(vinyl alcohol) (PVA) was studied. 1H‐NMR combined with a CAT technique was employed for the determination of the short branches. It was found that the formation of short branching is favorable at low concentrations of monomer, at high conversions, and at high temperatures. These facts evidently support the idea that the mechanism of the formation of short branching is back‐biting. Amounts of short branches in some commercial PVA were also estimated. The observed values lie in the range of 0.12–1.7 mole‐%.
Solution properties of phosphonitrilic fluoroelastomers
Authors: Carlson D. W. , O'Rourke E. , Valaitis J. K. , Altenau A. G. 
Published: April 2003

AbstractA series of phosphonitrilic fluoroelastomers which have excellent solvent resistance and low temperature flexibility, and which perform well under a broad range of service conditions, have been developed. The solution properties of one of these polymers were studied more extensively in order to develop suitable quality control procedures and to gain a better understanding of the polymer structure. Solvents for these procedures were established, fractionation procedures were developed, and intrinsic viscosity, osmotic pressure, and light‐scattering measurements were conducted. We found this polymer to have a very broad molecular weight distribution. And, although fractionation by molecular weight was effected, the fractions retained a broad molecular weight distribution. Our data do not indicate significant branching for this polymer. As a result of our studies, we have theorized that a supermolecular structure may be present in this polymer.
Effect of isotopic composition on free‐radical reactions in polyolefins
Authors: Milinchuk V. K. , Klinshpont E. R. , Vasilenko V. V. 
Published: April 2003

AbstractOn substitution of hydrogen by deuterium the radiation yield of free radicals in polyolefins decreases ca. 2‐fold. Under ultraviolet illumination (γ < 300 nm) in deuterated polyethylene (DPE), allyl radicals are converted into alkyl radicals (hfs constants a = 3.2 Oe, a = 4.4 Oe); in deuterated polypropylene (DPP), allyl and peroxide radicals are converted into alkyl radicals (a = 3.7 Oe). At 77°K under ultraviolet light in γ‐irradiated polyethylene (PE) and DPE, triene, tetraene, dienyl, trienyl, and tetraenyl radicals are formed. Deuterium substitution has no effect on absorption spectra of polyenyl radicals and polyenes. In polyolefins the quantum yields of photochemical reactions of allyl and peroxide radicals are 0.1–1.0. Photochemical reactions of peroxide radicals result in a radical concentration increase of ca. 3‐fold. In reactions of peroxide radicals in the dark, a kinetic isotope effect has been observed. Activation energies of substitution reactions of peroxide radicals are in PE, 9.3 ± 0.3 kcal/mole; in DPE, 10.2 ± 0.3 kcal/mole; in PP, 12.7 ± 0.4 kcal/mole; in DPP, 14 ± 0.5 kcal/mole. Possible mechanisms of the effect of polyolefin isotope composition on radical formation by high energy irradiation as well as on photochemical and dark reactions of free radicals are discussed. The effect of the energy released from phototransformations and radiationless deactivation of macroradicals on the migration of free valence is also considered.