This review describes polymerizations of dienes such as butadiene and isoprene with radical initiators, anionic initiators and transition metal complexes with respect to recent development. In radical polymerizations, living radical polymerizations are applied to polymerization of butadiene, and the living polymerization of butadiene gave narrow molecular weights and α, ω-difunctional polymers, leading to the formation of cyclic polybutadiene by ring closure reaction using both chain ends. In anionic polymerizations, functionalizations of polymers at the chain end and inchain have been developed by use of living anionic polymerization initiator and functional monomers. Many block copolymers including polybutadiene segment are synthesized and characterized. In transition metal complexes catalyzed polymerizations, a simultaneous control of 1, 4-cis selectivity and molecular weight of the polymers was achieved in the polymerization of butadiene. In the polymerization of isoprene, a precision polymerization is also achieved using lanthanide complexes. Cyclic polybutadiene was synthesized by ring opening metathesis polymerization (ROMP) of cyclooctadiene by the well designed Ru-based catalyst. The polymer obtained from ROMP consists of only 1, 4-structure.
