The Effect of Solvents on the Rate of Radical Polymerization of Ethyl Acrylate

Abstract

The polymerizations of ethyl acrylate initiated thermally by α, α'-azobis (isobutyronitrile)and photo-sensitized by α, α'-azobis (cyclohexanecarbonitrile) have been carried out at 30°C in various aromatic solvents. The thermal and photo-sensitized polymerization rates k_pth and k_pph respectively, changed markedly with solvents and increased in the order: toluene <b enzene<chlorobenzene<bromobenzene<o-dichlorobenzene. The rate of initiation k_i was determined by the inhibitor method using 2, 2-dipheny1-1-picrylhydrazyl as an inhibitor. The initiation rate was practically independent of these solvents in contrast to the change in the values of 2 k_t/k_p². The values of 2 k_t/k_p were obtained by the rotating sector method. The propagation rate constant k_p and termination rate constant 2 k_t were derived on the basis of the values of 2k_t/_p² and 2k_t/k_p. The k_p values changed markedly with the variation of solvents, while the 2k_t values changed a little. The remarkable change of k_p was considered to be dependent on the noticeable change in k_pdue to the interaction between solvents and propagating radicals. The interdependence between 2k_t and the viscosity of solvents could not be found.