Solvent effects on the free radical polymerization of styrene

Abstract

The free radical polymerization of styrene in various solvents has been studied. Using the rotating sector technique at 25°C rate coefficients for termination k_t and propagation k_p were determined. The linear decrease of the former with decreasing medium fluidity shows that termination is diffusion-controlled. Values of k_p decrease as the solvents used are increased in concentration. A similar trend in k_p is observed when polymerization is initiated thermally at 60°C. The solvent effect on k_t is similar to that previously recorded for methyl methacrylate, but solvents such as benzonitrile and diethyl malonate diminish k_p of styrene while they enhance k_p for methyl methacrylate.