Alternating copolymer of butadiene and propylene. IV. Studies on the catalysts for alternating copolymerization

The catalysts for alternating copolymerization of butadiene and propylene were investigated by means of ESR technique and potentiometric titration. It was found that several kinds of active species for the production of alternating copolymer, 1,2-polybutadiene, and trans-1,4-polybutadiene are formed, depending upon the catalyst composition of VO(acac)₂? Et₃Al? Et₂AlCl. ESR and potential titration studies suggest that the active species for alternating copolymerization is a divalent vanadium compound existing in an associated form.