Polymerization of conjugated diolefins by homogeneous aluminum alkyl‐titanium alkoxide catalyst systems. II. 1,2‐polybutadiene and 3,4‐polyisoprene

The polymerization of butadiene and isoprene by homogeneous aluminum alkyl‐titanium alkoxide catalysts is reported. Polybutadienes and polyisoprenes prevalently constituted of 1,2 and 3,4 units respectively were obtained. By fractionating the polybutadienes crystalline polymers with a syndiotactic structure were isolated; on the other hand, the polyisoprenes were found to be completely amorphous, probably because of lack of stereoregularity in the polymer chains. Some data concerning the copolymerization of isoprene with 1,3‐pentadiene are reported. A discussion of the dependence of the stereospecificity of the catalyst on the nature of the monomer and a model for the stereospecific synthesis of cis ‐1,4 isotactic polypentadiene are included.