Vinyl Chloride-Vinylidene Chloride Copolymerization: Kinetic Deviations and Structural Defects

The penultimate effect in the radical copolymerization of vinyl chloride (C) and vinylidene chloride (V), described in a previous paper, is interpreted in terms of head-to-head addition of a V molecule to a C-ended radical. The later is estimated from NMR analysis of the copolymer. It occurs about three times faster than the corresponding head-to-tail addition. It is shown that both the penultimate effect model and the “head-to-head assumption” lead to the same values for either the copolymer composition or several functions of the sequence distribution. It is further suggested that the head-to-head addition is possible owing to the propagation-depropagation equilibrium for the V-ended radical and to the very high reactivity of the tail radical produced.