Re-examination of free-radical copolymerization kinetics

The velocity of free-radical copolymerization is as yet not comprehensively understood in terms of the elementary processes of propagation and termination. A prevailing view of this classical subject may be that the propagation process is, in most cases, correctly described by the simple mechanism embodied by the “terminal model”, whereas the termination process involves complexity, still remaining to be interpreted. However, very recent experiments on styrene/methyl methacrylate and p-chloro-styrene/methyl acrylate copolymerizations, in which both the steady- and nonsteady-state polymerizations were observed to examine the two processes separately, indicate that the fact may be just the reverse: it is the propagation step that need be re-interpreted, while the termination step is well described by simple models such as the North “diffusion model”.