Polymerization of chloroprene. Part 4.—Influence of oxygen on the thermal reactions

Abstract

In order to evaluate critically experimental data on “thermal” polymerizations of chloroprene, a study of the polymerization of chloroprene monomer initiated by oxygenated chloroprene has been performed. Product analysis as a function of time indicates that in such oxygenated systems the polymer is formed exclusively from monomer, and that chloroprene dimers are simultaneously formed by parallel processes. The results suggest that the overall activation energy for the polymerization in oxygenated systems is smaller by several kJ than that reported for thermal polymerization in pure monomer; this implies that thermal polymerization in purified monomer can occur by some mechanism other than peroxide-initiated polymerization of monomer. The oxygenated systems have been studied in detail by a dilatometric method, and the kinetic results have been interpreted in terms of three parallel reaction types: (i) processes leading to the formation of dimers, uninfluenced by the presence of oxygenated monomer; (ii) a rapid polymerization process, which quickly decays because of consumption of the initiator; and (iii) a slower steady polymerization process. There is some evidence that the initiator in (ii) is a 1,2-polyperoxide of chloroprene.