Toru Arai

The effects of the bridge structure and the ligand system of zirconocene catalysts on the copolymerization of styrene and ethylene

The catalytic properties of zirconocene / MAO systems in the copolymerization of styrene and ethylene strongly depend on the structure of the zirconocene. An isopropylidene bridge leads to a relatively small bite angle and copolymers with a high styrene content. Fused ring substituents of cyclopentadienyl group such as indenyl or benzindenyl show remarkable effects on the styrene content, the catalytic yield and the molecular weights of the copolymers produced. Among the zirconocene complexes tested, rac-isopropylidenebis(45-benzindeny) zirconiumdichloride exhibits the best catalytic performance in the copolymerization. The zirconocene formed a novel styrene-ethylene random copolymer with isotactic stereoregularity and head to tail styrene-styrene structures. The C2 symmetry of the zirconocene is considered to be responsible for both the isotacticity and the formation of head to tail sequences.