SYNTHESIS OF STEREOREGULAR POLYMERS AND COPOLYMERS OF METHACRYLATE BY LIVING POLYMERIZATION AND THEIR CHARACTERIZATION BY NMR-SPECTROSCOPY

Highly isotactic and syndiotactic poly(methyl methacrylate)s (PMMAs) were prepared by living polymerizations in toluene with t-C4H9MgBr and t-C4H9Li-R3Al (Al/Li ≥ 2), respectively. Both tactic PMMAs have the same chemical structure from the left-end to the right-end of the polymer chain, and narrow molecular weight distribution. Stereochemical structures at and near the chain-ends of the isotactic PMMA could be identified with the aid of two-dimensional NMR spectroscopy. Structural investigation on the stereoregular oligomers of MMA by NMR and X-ray analysis provided important information on the stereoregularity of the initiation and termination processes. Block and random copolymers with high stereoregularity were prepared by these living polymerizations of MMA and ethyl methacrylate. Monomer sequence distribution and stereoregularity of the copolymers were studied by 13C NMR spectroscopy and the switching point of the block copolymer could be detected. Isotactic block and random copolymers of MMA and butyl methacrylate were also prepared and analysed by on-line GPC/NMR to give molecular weight dependence of the composition. The glass transition temperature of the copolymers of methacrylates was found to be altered in a wider temperature range by changing the tacticity as well as the composition.