摘要:

The kinetics of the formation of radicals from dibenzoyl peroxide supported on porous glass have been determined with EPR techniques over the temperature range of 25-100°C. Values of the activation energy of 18.5 and 25 kcal/mole have been observed for two differently prepared porous glass support materials.

ISSN:0022-233X    

DOI:10.1080/00222337008060972

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The values calculated for the side chain oscillator interaction energy for the polyene superconductor model have been revised. The use of parallel and perpendicular transitions gives a value for the naphthalene oscillator of 2.1 eV, well within the postulated range for a possibly operable effective interaction.

ISSN:0022-233X    

DOI:10.1080/00222337008060973

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A basic limitation in the processing of thermoplastics lies in the high viscosity of their melts. Since high viscosity is largely a consequence of high average molecular weight, this problem would be solved if a polymer could be provided in the form of polymer blocks which are essentially independent at elevated temperatures and which bond together reversibly at ambient temperatures. The theoretical possibility of achieving such a system is considered from the point of view of thermodynamic arguments as applied to an idealized system of monodisperse polymer blocks linearly connected by weak chemical bonds. Average molecular weights are expressed in terms of a molar Gibbs function contribution associated with a weak bond in the polymer. Assuming a requirement for substantial decomposition at 500°K, arguments are presented for an entropy contribution of ca. 200 J °K−1mole−1for such bonds, and on this basis an optimum weak bond energy of 60 ± 20 kJ mole−1is indicated. Possible block terminations giving energies of this magnitude are considered.

ISSN:0022-233X    

DOI:10.1080/00222337008060974

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

On the basis of a realization of thermodynamic requirements as given in part I, simple kinetic considerations are applied to the processes of weak bond fission and block recombination from two distinct bases: (a) independence of rate constants and viscosity (or average molecular weight) of the polymer system; and (b) a diffusion-controlled situation where the rate of block recombination is governed by the viscosity of the medium. On the independent rate constant model, an activation energy for the recombination process of less than 40 kJ [mole (of weak bonds)]−1gives an acceptable rate of equilibration at ambient temperatures; this criterion ought to be readily satisfied in practice. However, considerations of diffusion control suggest that equilibration may be too slow to be practicable and this is probably the major limitation on preparing rigid polymers with temperature-varying molecular weights

ISSN:0022-233X    

DOI:10.1080/00222337008060975

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The hydrogen bond is considered to be a special case of the oscillating ion bond (OIB bond).

ISSN:0022-233X    

DOI:10.1080/00222337008060976

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

ISSN:0022-233X    

DOI:10.1080/00222337008060977

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

ISSN:0022-233X    

DOI:10.1080/00222337008060978

出版商:Taylor & Francis Group    

年代:1970

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:10.1080/00222337008060961

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor