Coordination Polymerization (Styrene and Polar Vinyl Monomers)

Abstract

Polystyrene and poly(methyl methacrylate) (PMMA) are important commercial polymers which are produced by radical or anionic polymerization. Living radical or anionic polymerization enables us to control of the molecular weight and its distribution of these polymers. However, it is difficult to obtain a high-molecular-weight polymer with controlled microstructures, i.e., stereoregularity, using these polymerization methods. Early transition metal complexes catalyze the coordination-insertion mechanism to give highly stereoregular polymers with different physical properties compared with the corresponding atactic polymers. For example, highly syndiotactic polystyrene synthesized with coordination-insertion polymerization shows a high melting point (Tm, ~270 C) with fast crystallization rate and high chemical resistance. These properties enable it to be applied as engineering plastic materials. Isotactic polystyrene also possesses high Tm (~240 C), although the crystallization is relatively slow. The coordination polymerization of MMA also gives highly stereoregular PMMA under mild conditions, of which glass transition temperature (Tg) depends strongly on the stereoregularity. This chapter introduces representative catalyst systems for the coordination polymerization of styrene or polar vinyl monomers along with their polymerization mechanisms. Copolymerization of ethylene and polar vinyl monomers, which has been recently advanced, is also described.