Some Features of the Kinetics of Catalytic Copolymerization. Copolymerization in the Butadiene-Isoprene and Butadiene-Styrene Systems

In the course of research into carbon-chain polymerization under the influence of the acid-type catalysts, aluminum chloride, boron fluoride, stannic chloride, and others, a series of investigations have established the fundamental mechanisms of these chain processes, indicating that they have an ionic character. On the basis of this research, it was suggested that the active center in carbon-chain polymerization is a compound with a tervalent positive carbon atom at the end. The kinetics of catalytic copolymerization had not been studied until the present. There has been only a little work published in connection with determining the composition of copolymers and calculating the copolymerization constants for the systems in question. We initiated some research into the dependence of the speed of catalytic copolymerization on the composition of the original mixture, in conjunction with a determination of the speeds of separate polymerization of the monomers involved, since a comparison of data on the kinetics of copolymerization with that of separate polymerization gives a more complete representation of the mechanism of the process. A study was made of the speed of copolymerization of the systems : isoprene-butadiene and styrene-butadiene, and also of the kinetics of separate polymerization of these monomers. Polymerization was carried out in ethyl chloride with stannic chloride as the catalyst, at 0° C, by the dilatometric method.