摘要:

To investigate the method of measurement of the initiation rate constant in cationic polymerization, styrene and α-methylstyrene are polymerized by triphenylmethyl stannic pentachloride (Ph3CSnCl5). Adding these monomers to a solution of Ph3CSnCl5, the strong absorption of triphenylmethyl cation at 400 to 450 mμ disappears. The rate of disappearance of the absorption at 430 mμ is proportional to the concentration of Ph3CSnCl5and monomer. It is confirmed that this disappearance of the absorption is due to the conversion of triphenyl cation to styryl or α-methylstyryl cation. Therefore, the rate of consumption of triphenylmethyl cation corresponds to that of the addition of triphenylmethyl cation to the olefinic double bond in a monomer, that is, the rate of the initiation reaction. Considering the dissociation constant of Ph3CSnCl5, the initiation rate constants of styrene and α-methylstyrene in ethylene chloride solution at 30°C are 11.6 × 10−2and 2.85 liters/mole-min, respectively. These values seem to be much smaller than the propagation rate constant of each monomer. However, the effect of polymerization conditions, for example, the kind of a monomer and the polarity of a solvent, on the initiation rate constant is the same as in the propagation reaction. This fact suggests the similarity of a reaction mechanism in both elementary reactions.

ISSN:0022-233X    

DOI:10.1080/10601326708054004

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The Tobolsky-Eisenberg theory serves to explain the equilibrium polymerization of sulfur in terms of the dependence of S8(ring) concentration on temperature and the dependence of number-average degree of polymerization on temperature. The predictions of the theory are completely in accord with experiment. In this paper it is shown that it is possible to take the presence of another component in the melt, Sπ, into account, using a slightly modified version of the Tobolsky-Eisenberg theory. When this is done it is found that the earlier conclusions remain valid. The molecular complexity and structure of Sπ is also discussed.

ISSN:0022-233X    

DOI:10.1080/10601326708054005

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The intrinsic viscosities of sodium and potassium poly(styrene sulfonates) having different molecular weights were determined in sodium and potassium chloride solutions of various concentrations. The data were analyzed on the basis of the theory of Stockmayer and Fixman and the values of the mutal excluded volume of segments determined. The values obtained have been compared with those calculated using Ptitsyn's theory of excluded volume. To achieve semiquantitative agreement between theory and experiment, the effective and not the nominal charge of polyions has to be used in calculations. From the intrinsic viscosities the molecular expansion was also determined and the values obtained compared with those given by Fixman's theory of polyelectrolytes. Finally, the temperature coefficients of the intrinsic viscosities of some solutions having different ionic strength have also been ascertained.

ISSN:0022-233X    

DOI:10.1080/10601326708054006

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The energy distribution of a monoenergetic incident neutron beam after a single scattering event provides information concerning the molecular motions of a polymer in the region 800 to 30 cm−1. In polyethylene (Marlex 6050) several peaks are observed in the neutron spectrum between 200 and 600 cm−1. The frequencies corresponding to these peaks are in good agreement with those predicted from a calculation of the dispersion relations of the skeletal modes (bending and stretching) taking into account interchain forces. In the case of an oriented sample of the polymer, a polarization effect can be obtained by placing the momentum transferKof the neutron parallel or perpendicular to the chain directionS.This allows the identification of transverse and longitudinal modes of vibration. This effect has been studied in the case of polyethylene and polyoxymethylene. The frequency distribution of phonons, derived from the neutron data under certain approximations, were also obtained from samples of polyoxymethylene, polyacrylonitrile, and polyethylene glycol. These results are compared with the observed infrared and the calculated frequencies.

ISSN:0022-233X    

DOI:10.1080/10601326708054007

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

The theory of elasticity of polymer networks has been developed along two lines. The phenomenological approach leads to the Mooney-Rivlin relation between stress and extension ratio for uniaxial extension. The statistical theory of elasticity, based on a model for polymer molecules, predicts a similar relation with one of the constants zero. Actual elastic properties of rubbers do not agree fully with either theory.

ISSN:0022-233X    

DOI:10.1080/10601326708054008

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0022-233X    

DOI:10.1080/10601326708053993

出版商:Taylor & Francis Group    

年代:1967

数据来源: Taylor