|Fundamental Studies and Recent Advances in Anionic Polymerization 3.
Molecular Design of Elastomers by Means of Living Anionic Polymerization
Polymeric and Organic Materials Department, Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan
Nippon Gomu Kyokaishi,(2007),80(2),59-65 General Review in Japanese
This paper will review various molecular designs and syntheses of synthetic elastomers by means of living anionic polymerization of 1,3-diene monomers such as 1,3-butadiene and isoprene. By appropriately choosing polymerization variables such as initiator, solvent, temperature, concentration, and additive, a wide variety of poly(1,3-butadiene)s and poly(isoprene)s with precisely controlled chain-lengths as well as desired microstructures have been available. Furthermore, random copolymers of styrene-1,3-butadiene rubber (SBR) and styrene-1,3-butadiene-isoprene rubber (SBIR) and ABA triblock copolymers of polystyrene-block-poly-1,3-butadiene-block-polystyrene (SBS) and polystyrene-block-polyisoprene-block-polystyrene (SIS) have been industrially produced at the present time. The latter block copolymers are well known as thermoplastic elastomers where each segments are phase-separated and self-organized at molecular level and the polystyrene segments self-organized work as physically cross-linked points. Well-defined chain-end-functionalized poly-1,3-butadiene and polyisoprene with hydroxyl groups at both chain-ends (one hydroxyl group per each chain-end) are synthesized by living anionic polymerization and used as model network elastomers. It has been found that the introduction of polar functional groups such as amino and hydroxyl groups into synthetic elastomers can affect significantly on their physical properties. We have recently established a novel methodology based on living anionic polymerization using specially designed 1,1-diphenylethylene derivatives, by which multi-functionalization is possible at polymer chain-ends and/or in-chains. We have also demonstrated several possibilities of new synthetic elastomers such as chain-end-multi-functionalized poly-1,3-dienes, regular and asymmetric star-branched polymers comprised of poly-1,3-diene segments, and star-branched block copolymers of styrene and 1,3-diene monomer, all of which can be synthesized by the above-mentioned methodology.
Living Anionic Polymerization, Synthetic Elastomers, Microstructure, Block and Random Copolymers, Chain-end-multi-functionalized Polymers