The Effect of Solvents on the Rate of Radical Polymerization of Methyl Methacrylate

Abstract

The polymerizations of methyl methacrylate (MMA) initiated thermally by α, α′-azobis (isobutyronitrile) (AIBN) and photosensitized by α, α′-azobis (cyclohexanecarbonitrile) (ACN) have been carried out in various solvents. The thermal and photosensitized polymerization rates (R_pth and R_pph, respectively) changed markedly and increased in the following order with respect to solvents 1, 1, 1-trichloroethane < toluene < benzene < ethylbenzene < 1, 2-dichloroethane < anisole < o-dichlorobenzene < benzonitrile < 1, 2, 4-trichlorobenzene < 1, 1, 2, 2-tetrachloroethane < benzyl alcohol. The rate of initiation (Ri) was practically independent of these solvents in contrast to the changes in the values of 2k_t/k_p². The values of 2k_t/k_p were obtained by means of the rotating sector method. The propagation rate constant (k_p) and termination rate constant (2k_t) were derived on the basis of the values of 2k_t/k_p² and 2k_t/k_p. The k_p values changed slightly in these solvents, but the change was less than those of R_pth and R_pph. The values of 2k_t changed in these solvents, and were found to be nearly proportional to the inverse of the viscosity of the monomer-solvent mixture.