Recent developments in lanthanide catalysts for 1,3-diene polymerization

Lanthanide catalysts are typical for the cis polymerization of 1,3-dienes. The ternary system AlEt2Cl - Nd(OCOR)(3) - Al(iBu)(3) (R = alkyl group) is now used for the commercial production of cis polybutadiene. The effect of catalyst component addition order on activity and heterogeneity has been examined. In the ternary systems, only part of the lanthanide (Ln) is active in the catalysis. Much more active systems are obtained using allyl derivatives of Nd, Pr, Gd, in combination with methylaluminoxane (MAO). Evidence is reported suggesting that Ln catalysts have an ionic structure. Ln catalysts are also active for the polymerization of substituted butadienes and give cis-isotactic polymers from terminally substituted monomers.