Effect of alkylaluminium on the regio- and stereoselectivity in copolymerization of isoprene and butadiene using TiCl4/MgCl2 type Ziegler-Natta catalyst

Alkylaluminium compounds with smaller alkyl group size showed higher copolymerization activity, higher reducing ability and then yielding more active center numbers ([C*]/[Ti]) in the order TEA > TiBA > DiBAH > DEAC. The copolymers obtained during the very initial period were the mixtures of cis-1,4 units and trans-1,4 units structures and then transformed to highly trans-1,4 structure, indicating a transformation of the active center nature during the early polymerization stage, which can be accelerated effectively through the addition of DEAC into the TiCl4/MgCl2-TEA catalyst system.