bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radical polymerization of metal‐coordinated monomers with ligands of pyrrole‐containing schiff bases
Authors: Tsuchida Eishun , Tomono Tsugikazu , Honda Kenji 
Published: April 2003

AbstractThe copper complexes and the cobalt complex with the ligand of 3‐(2‐pyrrolylmethyl‐enimino)propene‐1 (PIP) or p‐(2‐pyrrolylmethylenimino)styrene (PIS) were synthesized and homopolymerizations and the copolymerization with styrene, acrylonitrile, methyl methacrylate and acrylic acid studied. In the polymerization of chelate monomers, inhibition of radical polymerization by the central metal ion was observed, but the chelate polymer could be obtained only if the initiator was present in higher concentrations in the feed. It is considered that the strength of inhibition depends on the electronic configuration of d‐orbitals of the central metal ion. The initiation mechanism of the cupric chelate monomer may be reduction of the metal ion by the redox reaction with a primary radical via the intramolecular electron transfer through the π‐conjugated system of the ligand prior to the propagation step. This mechanism was verified by studying the redox reaction of various copper complexes with DPPH. In the system of the copper complex containing PIS and acylic acid the alternating copolymer could be obtained at any mole fraction of monomer mixture in feed.
Cyclopolymerization of isoprene with VCl4–AlEt2Br catalyst system
Authors: Gandhi V. G. , Deshpande A. B. , Kapur S. L. 
Published: April 2003

AbstractIsoprene was polymerized at 30°C with VCl4–AlEt2Br catalyst system in n‐hexane. A linear dependence of rate of polymerization on the monomer and catalyst concentrations was found. The overall activation energy was 8.96 kcal/mole. Infrared spectra of polyisoprene showed the presence of cyclic structure, indicating a cationic mechanism of polymerization.
Absorption of polymers at the solution–solid interface. XII. Stabilization of dispersed silica by absorbed styrene–methyl methacrylate copolymers
Authors: Barron M. J. , Howard G. J. 
Published: April 2003

AbstractThe ability of styrene–methyl methacrylate copolymers to stabilize silica dispersions has been investigated. Random, block, and graft copolymers covering the entire composition range have been employed in carbon tetrachloride, trichloroethylene, and benzene solutions. Equilibrium sediment volumes and dispersion turbidities provide adequate and concordant estimates of stabilization efficiency. Polystyrene is not adsorbed by precipitated silica from trichloroethylene or benzene and does not stabilize dispersions in these liquids; although adsorbed from carbon tetrachloride, there is no stabilization. Poly(methyl methacrylate) is an efficient dispersion stabilizer, and its performance is independent of molecular weight over a wide range. Random copolymers having styrene contents in excess of ca. 60% do not stabilize in trichloroethylene but do so in carbon tetrachloride, although well adsorbed in both cases. With this major exception, and that of a low‐styrene graft copolymer in carbon tetrachloride, copolymers of all structures and compositions stabilize well, better than poly(methyl methacrylate) in the solvents examined. A substantial degree of surface coverage is necessary for optimum stabilization. Subsidiary solution adsorption and layer thickness measurements are also reported.
Modification of poly(vinyl chloride). XXIV. Graft polycondensation of p‐(2‐chloroethyl)thiophenol on poly(vinyl chloride)
Authors: Mori Kunio , Nakamura Yoshiro 
Published: April 2003

AbstractA new graft reaction, the graft polycondensation of p‐(2‐chloroethyl)thiophenol (CETP) onto poly(vinyl chloride) (PVC) in ethylenediamine (EN) and its mixed solvents was studied under various graft conditions. Two graft procedures which is different with addition operations of CETP were tried. The per cent grafting G and the grafting efficiency E in procedure A were generally higher than those in procedure B. G and E also increased with increase in temperature and time. The increase of the weight of PVC and in the concentration of CETP increased G and E, respectively. Mixed solvents composed of EN and benzene, tetrahydrofuran, or dimethylformamide also increased G and E. The grafted products thus obtained have a gel fraction and contain nitrogen. However, on grafting in the presence of C12H25SH, higher G′ and E′ were obtained, and the products contained no gel fraction or nitrogen. The degree of polycondensation and the number of grafts in the grafted PVC were about 4–12, and 0.64–1.71 mole‐%, respectively, as estimated from elemental analysis.
Structure and reactivity in cationic polymerization of butadiene derivatives. II. 1‐phenylbutadiene
Authors: Masuda Toshio , Otsuki Michihisa , Higashimura Toshinobu 
Published: April 2003

AbstractThe reactivity of 1‐phenylbutadiene (1‐PBD) in cationic polymerization and the monomer structure were investigated. 1‐PBD polymerized at −78°C in several solvents initiated by cationic catalysts such as stannic chloride and tungsten hexachloride. The polymerizations proceeded predominantly via 3,4‐type propagation mode, and gave low molecular weight polymers. More than one double bond of 1‐PBD was consumed during the polymerizations, probably due to transfer and cyclization reactions. 1‐PBD was several times as reactive as styrene and trans‐1,3‐pentadiene in copolymerizations. The Hammett plots of reactivities of ring‐substituted 1‐PBD in cationic polymerization gave the p‐value of ‐1.20, which is 0.6 times that of styrene. The 1H and 13C NMR chemical shifts of ring‐substituted 1‐PBD were measured and discussed in relation to the reaction mechanism.
Effect of polymer on electron‐donating character of polymer donor. II. Formation of charge‐transfer complex between polymers containing N‐dimethylaniline group and trinitrotoluene
Authors: Iwatsuki Shouji , Inukai Ken‐Ichi 
Published: April 2003

AbstractFormation of charge‐transfer complexes with trinitrotoluene (TNT) as a common acceptor was studied in detail by using dimethyltoluidine (DMT), poly‐N‐dimethyl‐p‐aminostyrene (poly‐ASt), and also copolymers of aminostyrene (ASt) and styrene (St) as donors. A smooth bathochromic shift in λmax was observed with increasing ASt unit content in copolymers. Values of the constant for charge transfer complex formation KCT were found to increase smoothly with ASt unit content. However, the KCT value with DMT did not coincide with the value extrapolated from the plot of KCT value versus ASt unit content to zero ASt unit content, but was found to be much higher than the limiting value, in contradiction to the results obtained with maleic anhydride (MAnh). The entropy of complex formation with DMT was found to be exceptionally small; this small value may be responsible for the high KCT value with DMT.
γ‐radiolysis of ketone polymers. III. Copolymers of ethylene and carbon monoxide
Authors: Slivinskas J. A. , Guillet J. E. 
Published: April 2003

AbstractThe γ‐radiolysis of copolymers of ethylene and carbon monoxide (CO‐PE) containing 0–9 wt‐% of CO has been studied in the solid phase under vacuum with respect to hydrogen production, scission, and crosslinking. In this regard, the introduction of carbonyl groups into polyethylene increased both the scission and crosslinking efficiency. However, a theoretical statistical treatment for random scission and crosslinking, which was used to calculate G(s) and G(x) yields, predicted gelation with irradiation dose; this was confirmed experimentally. The increased G(x) values are attributed to the localization of absorbed energy in the carbonyl group arising from preferential trapping of thermalized secondary electrons. A stoichiometric balance is shown to be consistent with the reduction of one carbonyl group to a secondary alcohol per excess crosslink observed. The G(H2) yield is reduced by the presence of ketone groups to a level which is in close agreement with the yield obtained for the model ketone 12‐tricosanone. This quenching of H2 production is explained by intramolecular electronic energy transfer along the chain to the carbonyl group with concomitant intermolecular charge transfer between neighboring molecules.
TGA–MS degradation studies of some new aliphatic–aromatic polybenzimidazoles
Authors: Tsur Yoel , Freilich Yitzchak L. , Levy Moshe 
Published: April 2003

AbstractThe degradation of a series of polybenzimidazoles containing metylene groups in the chain was studied by TGA and MS. On heating the polymer derived from m‐phenylenediacetic acid and 3,3′‐diaminobenzidine to about 560°C in argon, partial fast decomposition into a solid sublimate was observed. The sublimate consisted of a mixture of fractions derived from the breaking of the chain at the methylene bonds. These methylene groups can be preoxidized at 250°C to carbonyl groups, eliminating thereby this mode of decomposition. At temperature higher than 560°C, gaseous products similar to those of the corresponding all‐aromatic PBI are obtained.
Photolysis of poly(ethyl acrylate) and poly(n–butyl acrylate) in vacuo
Authors: McGill W. J. , Ackerman L. 
Published: April 2003

AbstractThin films of poly(ethyl acrylate) and poly(n‐butyl acrylate) were decomposed in vacuo by means of a high pressure Hg lamp, and the rate of development of volatile products was measured. The main gaseous products were CO, CO2, and the alcohol, aldehyde, alkane, and formate derived from the respective ester groups. In addition poly(ethyl acrylate) evolved acetal as well as ethyl propionate, while n‐butyl valerate was evolved from poly(n‐butyl acrylate) only after prolonged exposure. All products and the principal features of the decomposition are discussed.
ESCA investigation of the electronic structure of polyhexafluorobut‐2‐yne
Authors: Chambers R. D. , Clark D. T. , Kilcast D. , Partington S. 
Published: April 2003

AbstractPolyperfluorobut‐2‐yne is prepared by a fluoride ion‐induced polymerization of hexafluorobut‐2‐yne. The mass spectrum indicates a regular fragmentation pattern but the ESCA spectrum establishes the structure as a polyene, rather than a crosslinked system, and the occurrence of a shake‐up peak assists in this assignment.
Preparation and characterization of alternating copolymer of α‐methylstyrene and acrylonitrile made with zinc chloride–peroxide catalysis
Authors: Kuntz Irving , Chamberlain Nugent F. 
Published: April 2003

AbstractThe copolymerization of the zinc chloride complex of acrylonitrile in excess acrylonitrile with α‐methylstyrene in the presence of lauroyl peroxide is described. Elemental and proton NMR analyses indicate the equimolar nature of the copolymer product. 13C NMR examination shows that this copolymer is alternating in structure and suggests that the steric placements of the copolymer are random in nature; that complexation does not lead to a stereoselective enchainment mode is the implication of our results. A copolymer which appears to be similar to our product has been prepared by other workers using Al(C2H5)1.5Cl1.5 complexation. Our conclusions regarding copolymer stereoregularity differ from theirs.
Preparation and photolysis of poly‐p‐methoxyacrylophenone and its copolymers with styrene and methyl methacrylate
Authors: Lukáč I. , Moravčíak M. , Hrdlovič P. 
Published: April 2003

AbstractPoly‐p‐methoxyacrylophenone (PPMeOAP) and its copolymers with styrene (PMe‐OAP–S) and with methyl methacrylate (PMeOAP–MMA) were prepared. The photolysis in solution with 313 and 366 nm radiation was followed viscometrically. In solvents such as chlorobenzene and ethyl benzoate, random main‐chain scission from n–π* excited triplet state occurs. The lowest excited triplet state in formic acid and in ethylene chlorhydrin is of the character π–π*, from which no main‐chain scission occurs. In solvents in which destruction occurs, the main‐chain scission is retarded by triplet quenchers, such as naphthalene, 2,5‐dimethyl‐2,4‐hexadiene, and biphenyl. Quenching experiments indicate that the lifetime for the excited triplet state of PPMeOAP is 25 times that for polyacrylophenone. In PMeOAP–MMA copolymers, quantum yields of main‐chain scissions were lower and lifetimes of excited triplets were longer than in PPMeOAP, due to hindered intramolecular photoreaction.
Structure–property relationships in polyamides containing cyclohexylene or phenylene structures
Authors: Ridgway James S. 
Published: April 2003

AbstractPolyamides were prepared from linear, aliphatic dicarboxylic acids of six to twelve carbon atoms with 1,4‐cyclohexanebis(methylamine), 1,4‐cyclohexanebis (ethylamine), p‐xylylenediamine, and p‐phenylenebis(ethylamine). Melting points, glass transition temperatures, densities, and moisture regains were compared for the polymers to determine the relative effect of the cyclohexylene and phenylene linkages. While polyamides containing the trans‐cyclohexylene group possessed higher glass transition temperatures than their aromatic counterparts, melting behavior was not as consistent. The odd‐even rule, which states that polyamides with an even number of methylene linkages between the ring and the functional group melt higher than those with an odd number of such linkages, was violated in the cycloaliphatic systems. The Tg of ring‐containing polyamide fibers was not dependent solely upon ring concentration, but was influenced by the molecular fit of the ringed intermediate in the polymer chains. Molecular fit appears to affect the Tg and melting point of alicyclic polyamides to a greater extent than the aromatic analogs. Differences in Tg, both within and among the polymer series, was not explained by either density or the degree of crystallinity.
Radiation‐induced emulsion copolymerization of tetrafluoroethylene with propylene. III. Polymerization mechanism
Authors: Suzuki Nobutake , Matsuda Osamu , Okamoto Jiro 
Published: April 2003

AbstractIn the radiation‐induced emulsion copolymerization of tetrafluoroethylene with propylene, the dose rate dependence, the effect of emulsifier concentration, and the effect of monomer composition were studied. The rate of polymerization was proportional to the 0.90 power of the dose rate and the 0.26 power of the emulsifier concentration. The degree of polymerization was independent of the dose rate and the emulsifier concentration. Both the rate of polymerization and the degree of polymerization increased with tetrafluoroethylene content in the monomer mixture. The resulting copolymer was an alternating polymer over a wide range of monomer composition. It was concluded from the dose rate dependence of the rate of polymerization that the emulsion copolymerization is mainly terminated by degradative chain transfer of the propagating radical to propylene.
Structure and reactivity in cationic polymerization of butadiene derivatives. III. 2‐phenylbutadiene
Authors: Masuda Toshio , Mori Toshiaki , Higashimura Toshinobu 
Published: April 2003

AbstractCationic polymerization of 2‐phenylbutadiene (2‐PBD) has been investigated. Polymerization were performed by SnCl4·TCA, WCl6, and BF3·OEt2 as catalysts in methylene chloride. 2‐PBD polymerized easily and gave low molecular weight polymers. The polymerization proceeded to give a polymer having 1,4‐structure without 1,2‐ or 3,4‐structure. The double bonds of the polymer were partially consumed, probably owing to cyclization and chain‐transfer reactions. 2‐PBD was 0.66 times as reactive as styrene and 1.2 times as reactive as isoprene in the copolymerization at −78°C by SnCl4·TCA in methylene chloride. Reactivities of ring‐substituted 2‐PBD obeyed the Hammett relation with ρ+ = −2.04. The 13C chemical shift of ring‐substituted 2‐PBD was measured. Chemical shift values for C1 and C3 were correlated with Hammett σ, but those for C2 and C4 were almost unaffected by the substituents. On the basis of experimental results, the transition state of the cationic polymerization of 2‐PBD was depicted as a benzylic cation rather than a phenylallylic one.
Interaction of monovalent and divalent counterions with some carboxylic polysaccharides
Authors: Rinaudo M. , Milas M. 
Published: April 2003

AbstractEleven samples of carboxylic polysaccharides were studied. The activity coefficients γ have been measured for monovalent (Na+) and divalent (Ca2+) counterions. There is no specific influence of the structure of the chain on γ values. Agreement with theoretical values confirms the rigidity of the chain; for low charge density, the theoretical treatment seems to be incorrect. Selectivity is discussed in term of selectivity coefficient K and free energy of exchange ΔG; ΔG is linearly related to the charge density but K which characterizes the competition of the two counterions is sensitive to the nature of the chain. The carboxymethylamyloses present a larger selectivity whose origin is not discussed here. The last point treated is the intrinsic constant of dissociation of polyacids. The pK0 values are practically independent of the nature of the polyelectrolyte and of the charge density; the values are close to the pK0 of monomeric unit and are not affected by the position of COOH in the anhydroglucose ring.
Interaction of organo‐alkali compounds with unsaturated hydrocarbons
Authors: Podolsky A. F. , Taran A. A. 
Published: April 2003

AbstractThe stability of disodium tetramer of α‐methylstyrene (“living” polymer) in THF and in a THF‐α‐methylstyrene mixture has been investigated by spectrophotometry. It was found that at 25°C and at concentrations lower than the equilibrium concentration α‐methylstyrene greatly stabilizes the process leading to disappearance of the main absorption band (λmax = 340 mμ) of “living” polymer. In this case isomerization of “living” polymer is accompanied by quantitative conversion of the compound having λmax = 340 mμ into a new compound with λmax = 430 mμ. The constants of the disappearance rate D340 and the activation energies of the process were determined in THF and in a THF‐α‐methylstyrene mixture. The introduction of small amounts of α‐methylstyrene into living polymer at 25°C markedly increases its activity in the course of propagation. The experimental results are considered from the standpoint of formation of complexes of living polymer with α‐methylstyrene.
Radiation‐induced crosslinking and cyclization in 1,2‐polybutadiene
Authors: Von Raven A. , Heusinger H. 
Published: April 2003

AbstractIn order to get information on the radiolytic changes in 1,2‐polybutadiene (1,2‐PB) the sol and gel fractions, the conversion of double bonds, the structure and concentration of radicals, the formation of dienes and the formation of gaseous products were measured. In addition, the dose rate dependence and temperature dependence for the conversion of double bonds were determined. G values for double bond conversion depend on molecular weight and range from 20 to 200. G values for crosslinking are about 10. A mechanism for the double bond conversion is proposed which involves initiation by a transformation of the primary radical ion in the vinyl group into a carbonium ion and a radical. This is supported by ESR measurement. Reaction of the carbonium ion with a vinyl group in the same chain gives rise to cyclization, whereas reaction with a vinyl group in a neighboring chain results in crosslinking. A comparison of the G values for conversion of double bonds with the G values for crosslinking shows that the formation of cyclic rings exceeds the formation of crosslinks by a factor of about 10. The corresponding values in 1,4‐cis‐ and 1,4‐trans‐polybutadiene are much smaller [G(cl) ≃ 2; G(db) ≃ 7]. The pendent vinyl groups in 1,2‐polybutadiene therefore are more reactive than the vinylidene groups in 1,4‐polybutadienes.
Metal compounds in free‐radical processes. III. Polymerization of acrylonitrile initiated by copper (II) nitrate in presence or absence of triphenylphosphine
Authors: Bartoň J. , Vlčková J. , Ondrejovič G. , Gažo J. 
Published: April 2003

AbstractThe bulk polymerization of acrylonitrile (AN) initiated by copper (II) nitrate, Cu(II), in the absence of light has been studied. The rate of the AN polymerization may be expressed in the Cu(II) concentration range from 5 × 10−4 to 1 × 10−1 mole 1.−1 by the equation, Rp = k5[Cu(II)]0.68, where k5 = KAN[AN]/(1 + KAN[AN]). From the spectrophotometric measurements the values of 0.70 l./mole and 0.08 l, mole were obtained for the equilibrium constant at 20 and 60°C, respectively, KAN = [C]/[AN]‐[Cu(II)], corresponding to the formation of the complex C from acrylonitrile and copper (II) nitrate. An addition of triphenylphosphine (C6H5)3P into the polymerization system reduces Rp, and no polymerization takes place at all provided [(C6H5)3P]/[Cu‐(II)] ≧ 5. The retardation effect of (C6H5)3P on the polymerization of AN initiated by Cu(II) is attributed to a competitive reaction of Cu(II) with (C6H5)3P in which Cu(II) is reduced and the product of this reduction CuNO3·2(C6H5)3P is inactive with respect to the polymerization of AN.
Reactions of models of the growth center during anionic polymerization of methacrylate esters
Authors: Lochmann L. , Rodová M. , Petránek J. , Lím D. 
Published: April 2003

AbstractReactions of α‐lithioisobutyric acid esters were studied as models of partial reaction taking place during anionic polymerization of methacrylate esters. The rates of selfcondensation reactions and condensations with nonmetalated esters were determined for these models. In both cases ketoesters were the final products. Besides esters of α,α,α′‐trimethylglutaric acid expected according to Michael's reaction scheme the addition of methacrylate esters to α‐lithio esters also yielded oligomeric compounds due to repeated addition of methacrylate esters. The α‐lithio oligomers of methacrylate esters underwent cyclization condensation which gave rise to esters of substituted cyclohexanonedicarboxylic acids. The alkali metal alkoxides slowed down all the condensation reactions of α‐lithio esters investigated here. Such effect of alkoxides also appeared in the cyclization condensation of compounds formed by repeated addition of methacrylate esters, because in the presence of alkoxides the reaction mixture contained a higher amount of higher molecular weight compounds than in a system without alkoxide. The effect of alkoxides observed here is in accordance with the view that the cyclization condensation is one of the termination reactions of the anionic polymerization of methacrylate esters.
Thermal degradation of chlorinated rubber: Evidence for an alternative cyclic structure for chlorinated rubber
Authors: Dodson B. , McNeill I. C. 
Published: April 2003

AbstractThe thermal degradation under vacuum or in nitrogen of commercial chlorinated rubber (ICI Alloprene, 64.5 wt.‐% chlorine) was studied by isothermal thermogravimetry and by simultaneous TG/TVA with programmed heating by using a Cahn RG thermobalance built into a thermal volatilization analysis (TVA) system. Analysis of volatile products was performed by titration and by spectroscopic methods. The only major degradation product is hydrogen chloride; five‐sevenths of the total available hydrogen chloride is lost with great ease, and complete dehydrochlorination is very much easier than in poly(vinylidene chloride). Conjugation develops early in the degradation, but the minor products methane, ethylene, and hydrogen are observed in the later stages of reaction. These features cannot be reconciled with the previously proposed cyclic structure for chlorinated rubber, and an alternative structure which accounts well for the degradation behavior is suggested.