PROPAGATION AND TERMINATION PROCESSES IN THE FREE-RADICAL COPOLYMERIZATION OF METHYL-METHACRYLATE AND VINYL-ACETATE

The propagation and termination processes in free-radical copolymerization were examined on the basis of a complete set of experimental data carefully obtained for the bulk copolymerization of methyl methacrylate (MMA) and vinyl acetate (VAc) at 40-degrees-C by use of the rotating-sector technique. The composition curve conformed to the terminal model within experimental error. However, a moderate penultimate-unit effect was observed for the terminal MMA radical (s1 = k211/k111 = 0.4 +/- 0.2), in conformity to the prediction of the stabilization energy model. The concentration of the terminal VAc radical was too small to elucidate the details about this radical. The termination process in this system conforms to the notion of diffusion control, but the North diffusion model was found inadequate. Alternative, simple, no-parameter models were proposed, which described the experiments better.