On structural characteristics of stereoregular cis‐polybutadienes

Abstract The study of molecular weight distribution and the degree of branching on cis‐poly‐butadienes obtained by using complex catalysts Til4 + (i C4H9)6Al (I) and (i C4H9)2AlCl + CoCl2 (II) has established that the structural characteristics of these polymers do not depend exclusively on the type of catalyst used. The polymers obtained in the presence of catalyst II having a narrow molecular weight distribution at the beginning of the polymerization process become highly polydisperse towards the end of the reaction. This result as well as the increase in chain branching of the type II polymers at high degrees of conversion suggest interchain reactions to occur readily in the course of polymerization. In the case of type I polymers a narrow molecular weight distribution is observed; the polymerization having a stationary character during all its stages at 25°C. At lower temperatures, however, this character is disturbed, the polymer molecular weight increasing with the increase in conversion degree. Type I polymers are practically linear upto 100% conversion. Thus, both branching and molecular weight distribution of these polymers depend on polymerization conditions, affecting them differently for the two catalysts used.