摘要:

Application of the gas-liquid chromatographic method to the analysis of the process of styrene-acrylonitrile radical copolymerization, especially with a monomer mixture rich in styrene, provided evidence for penultimate and antepenultimate effects. Methods are given for the determination of the corresponding reactivity ratios:

ISSN:0022-233X    

DOI:10.1080/10601326708053736

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Theories dealing with the problem of termination in ionic polymerizations by hydride transfer coupled with allylic stabilization have been examined and extended. It is postulated that cationic polymerizations in general terminate with the irreversible destruction of growing ions by the following mechanism:

ISSN:0022-233X    

DOI:10.1080/10601326708053737

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The effect ofn-alkenes, i.e., propylene, 1-butene, 1-pentene, 1-hexane, and 2-octene, on the yield and molecular weight of polyisobutene obtained with AlCl3catalyst inn-pentane solvent at −78°C has been investigated. It has been found that the lower 1-alkenes are pure poisons; i.e., they decrease the yield (rate poisons) but do not affect product molecular weight. The rate-decreasing effect ofn-alkenes has been treated quantitatively by poison coefficients and their numerical values correlated with relative carbonium ion stabilities using the allylic termination concept. The mild molecular weight decreasing effect of 2-octene has been attributed to moderate transfer activity. The effect of temperature on the poison coefficients of 2-octene has been investigated and some insight into the activation energies of various elementary steps has been gained.

ISSN:0022-233X    

DOI:10.1080/10601326708053738

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The effect of branched alkenes on the rate (yield) and molecular weight of polyisobutene has been investigated. Monosubstituted branched ethylenes, i.e., 3-methyl-1-butene, 3,3-dimethyl-1-butene, and 4-methyl-1-pentene, were found to be virtually inert and did not affect the polymerization of isobutene under our experimental conditions. 2,2-Disubstituted branched ethylenes, i.e., 2-methyl-1-pentene, 2-ethyl-1-hexene, 2,4,4-trimethyl-1-pentene, and 2,4,4-trimethyl-2-pentene, were rate poisons and strong transfer agents. The steric configuration of substituents in the vicinity of allylic hydrogens strongly influences the poison and transfer coefficients of these materials. These coefficients have been discussed quantitatively in terms of the allylic termination theory.

ISSN:0022-233X    

DOI:10.1080/10601326708053739

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The effect of various conjugated dienes, e.g., butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2,5-dimethyl-2,4-hexadiene, cyclopentadiene, 2-methylcyclopentadiene, and 1,3-hexadiene, on the rate of polymerization (yield) and molecular weight of polyisobutene has been investigated. The overriding effect of dienes is rate retardation (poisoning) and a lesser measure of molecular weight depression (transfer activity) (exception, 1,3-pentadiene). The effects have been expressed quantitatively with poison and transfer coefficients and their values have been discussed. The poison coefficients indicate that the order of stabilities of substituted allyl carbonium ions is

ISSN:0022-233X    

DOI:10.1080/10601326708053740

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The effect of aging on the Wichterle-Marek-Trekoval (WMT) solid cationic catalyst for isobutene polymerization has been investigated. It was confirmed that this complex catalyst gives high molecular weight polyisobutenes at high rates at relatively high temperatures. Aging for various times and temperatures the Al(O-s-C4H9)3/BF3component and the Al(O-s-C4H9)3/BF3/TiCl4final catalyst strongly depresses rates of polymerization but only slightly affects the molecular weights produced. Fastest rates and molecular weights are obtained with freshly prepared catalyst whose Ti/Al ratio is ∼ 0.3 at about 30% conversions. Rates and polyisobutene molecular weights obtained by the present authors were higher than those reported by the Czechoslovakian workers. These results are discussed in terms of cationic polymerization mechanism, and an explanation for the reduced rates and molecular weights produced with aged WMT catalysts is proposed.

ISSN:0022-233X    

DOI:10.1080/10601326708053741

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The monomer and configurational sequences of several radical copolymers between substituted styrenes and acrylates have been examined by analyzing the high-resolution NMR spectra with the previously reported treatment of the styrene-methyl methacrylate system. The analyses have led to the conclusion that the monomer sequence distribution is just as expected from the usual copolymerization theory withr1andr2.

ISSN:0022-233X    

DOI:10.1080/10601326708053742

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

Intrinsic viscosities of poly-L-glutamic acid at pH 8.8 and of poly-L-lysine at pH 3.2 in the presence of salts which are typically representative of lyotropic series are presented. Viscosities decrease continuously with increasing salt concentration and their temperature coefficients are negative. The ranking of cations and anions for decreasing the intrinsic viscosity of poly-L-glutamic acid and poly-L-lysine respectively, corresponds to the ranking for ion binding to isoelectric gelatin.

ISSN:0022-233X    

DOI:10.1080/10601326708053743

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The effect of several polyelectrolytes on the absorption spectrum of crystal violet (CV) has been studied over a wide range of pH. The following polymers were used: isotactic poly(methacrylic acid), PMAi; conventional poly(methacrylic acid), PMAc; a methacrylic acid (80%)-styrene (20%) copolymer, PMAS; and poly(styrene sulfonic acid), PSSA. Distinctly different effects were observed in the four cases. This has been interpreted in terms of a dependence of the degree and mode of binding of cationic dye molecules onto the polyacids on the hydrophobicity of the macroions.

ISSN:0022-233X    

DOI:10.1080/10601326708053744

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

A theory has been developed which predicts the minimum permeability that can be expected for a polymer filled with platelike particles. Models are also developed for the permeability of liquids through filled polymers when the liquid adsorbs or collects at the filler-polymer interface. Some of the cases discussed include different types of dispersions, orientation of filler particles, and the effects of filler aggregation. Permeability, especially of liquids, is extremely complex, and many different types of behavior can be expected.

ISSN:0022-233X    

DOI:10.1080/10601326708053745

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor