PROPAGATION AND TERMINATION PROCESSES IN FREE-RADICAL COPOLYMERIZATION OF STYRENE AND ETHYL ACRYLATE

The propagation and termination processes in free-radical copolymerization of styrene (1) and ethyl acrylate (2) in the bulk at 40-degrees-C were examined by the rotating-sector technique. A marked penultimate-unit effect was observed for the terminal radical 1 (s1 = 0.27), in conformity with the prediction of the stabilization energy model. The concentration of the terminal radical 2 in this system was too small for the details about this radical to be elucidated. The termination process conforms to the notion of diffusion control, but conclusively not to that of chemical control. The experimental data, however, were not described very accurately by the North diffusion model. An alternative simple, no-parameter model, conceptually analogous to the Ito-O'Driscoll model, was proposed and found to describe the experiments better.