Recent Developments of Organotransition-metal Catalysts for Polymerization
2. d-Block Transition Metal catalysts for Diene Elastomers
Shojiro KAITA
OM Chem-Tech. Co., Ltd./RIKEN, Cooperation Center, Saitama, Japan
Nippon Gomu Kyokaishi,(2004),77(11),393-396 General Review in Japanese

Diene elastomers, in particular, high cis polybutadiene (BR) and high cis polyisoprene (IR), are widely used as synthetic rubber. Industrially, Ziegler-Natta catalyst systems using Ni, Co, and Nd metals have been employed for the production of BRs which have high 1,4-cis contents (94-98%), but the molecular weight and molecular weight distribution of the resulting polymers in these systems can not be well controlled (MWD 3-4). Since homogeneous catalysts can better control molecular weight, d-block transition metal metallocene/MAO catalyst systems, e.g. , have been developed recently. In such "single-site" catalyst systems, cis-specific living polymerization (sharp MWD) of 1,3-butadiene have been realized. This article is a brief introduction of recent topics, including modification of the system. Mechanistic studies of the 1,4-polymerization of butadiene affected by organometallic catalysts are also described.

d-Block Transition Metal, Organometallic Catalyst, Metallocene Catalyst, Single-Site Catalyst, Diene Polymerization, Polymerization Mechanism