Highly Isotactic and Living Polymerization of Ethyl Methacrylate with t-C4H9MgBr in Toluene and the Preparation of Block and Random Copolymers with High Stereoregularity

Abstract

The polymerization of ethyl methacrylate (EMA) with t-C4H9MgBr in toluene at low temperature gave a highly isotactic polymer as in the case of living and highly isotactic polymerization of methyl methacrylate (MMA) with t-C4H9MgBr. Although the molecular weight distribution (MWD) of the poly(EMA) was bimodal, both species giving higher and lower molecular weight fractions contributed to the formation of highly isotactic block copolymers with bimodal MWD, indicating the living nature of both species. The polymerization of EMA with the living anion of isotactic PMMA formed with t-C4H9MgBr gave a highly isotactic block copolymer with unimodal MWD. This suggests that the multiplicity of active species observed in the polymerization of EMA with t-C4H9MgBr was caused by the initiation of EMA with t-C4H9MgBr. Conventional copolymerization of EMA and MMA afforded a highly isotactic copolymer with bimodal MWD, confirming the above consideration. 13C NMR spectrum of the copolymer indicated the comonomer sequence to be random. Glass transition temperatures of the isotactic and syndiotactic copolymers of EMA and MMA could be changed from 8 to 120°C by changing composition and tacticity.