POLYMERIZATION OF BUTADIENE WITH TRIALKOXYGADOLINIUM CATALYST SYSTEMS

Butadiene was Polymerized with trialkoxygadolinium [Gd(OR)3]-based Ziegler catalyst systems in hexane at 50-degrees-C. For example, the polymerization with Gd(neopenty]-O)3-Et3Al-Et2AlCl was completed in 5 h to give the high cis polybutadiene (cis % = 94 approximately 98%). The effects of steric hindrance of alkoxy ligands and preparation conditions of catalyst systems were investigated in detail. Gd(neopentyl-O)3 exhibited higher activity than gadolinium catalysts with n-pentoxy and isopropoxy ligands. The molar ratio of [Cl]/[Gd] affected the polymerization activity: the maximum yield was attained at [Cl]/[Gd]congruent-to 2, whereas the polymer yield was very low at [Cl]/[Gd] =0 or [Cl]/[Gd] greater-than-or-equal-to 5. On the basis of these results, properties of active species were also discussed. Copolymerization with styrene was attempted to elucidate the polymerization mechanism. However, the insertion of styrene units into polybutadiene hardly occurred in all the catalyst systems employed here. The coordination constant of styrene was evaluated, assuming that styrene was coordinated strongly with the active species.