Models for free-radical copolymerization propagation kinetics

The alternative models for copolymerization kinetics are critically examined using recent experimental and theoretical results - both from our own work, and from other recent studies - with the aim of identifying a suitable replacement for the terminal model as the basis of copolymerization kinetics. Based on the combined results of these studies, it is concluded that the explicit penultimate model should be adopted as the basis of free-radical copolymerization kinetics, and that the origin of this penultimate unit effect is likely to be the result of a number of factors, including polar interactions, radical stabilization effects, entropic effects and direct interactions. The implications of these results for copolymerization kinetics are discussed.