Simultaneous Control of Molecular Weight and 1,4-Cis Selectivity in the Polymerization of 1,3-Butadiene with N,N′-Diphenyl and 3,3′,5,5′-tetra-t-Butyl Substituted (Salen)Co(II) Complex

Controlled 1,4-cis specific polymerization of butadiene (Bd) with N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-diphenylethylenediaminato cobalt (1), in combination with methylaluminoxane (MAO) was investigated. 1/MAO catalyst showed the high activity for the polymerization of Bd. In the polymerization of Bd with 1/MAO catalysts in CH2Cl2 at −30°C, the molecular weight of the polymer increased linearly with an increase of polymer yield, and the line passed through the origin. Moreover, the molecular weight distribution of the polymer was narrow (Mw/Mn=1.29) and microstructure was a high 1,4-cis content (~98%). The results demonstrate that a simultaneous control of 1,4-cis selectivity and the molecular weight of the polymer can be achieved in the polymerization of Bd with the (salen)Co(II) having t-butyl groups at 3,3′,5,5′-positions in the aromatic ring and phenyl groups at N,N′-positions in combination with MAO.