THE TACTICITY OF THE BACKBONE CHAIN OF POLY(MACROMONOMER)S OF OMEGA-METHACRYLOYLOXYETHYL POLYSTYRENE MACROMONOMERS PREPARED BY RADICAL-CHAIN POLYMERIZATION

The effect of the polystyrene chain as a bulky long ester group of met hacrylate monomer on the chain tacticity was investigated in the radic al chain polymerization of omega-methacryloyloxyethyl polystyrene macr omonomers of different molecular weights. The macromonomers and 5-phen ylbutyl methacrylate (3PBMA), which corresponds to the unimer model of the macromonomer, were synthesized and polymerized with azobisisobuty lonitrile in benzene at 60 degrees C. The polymers obtained were conve rted to poly(methyl methacrylate)s by acid hydrolysis reaction followe d by methyl esterification with diazomethane to estimate the chain tac ticity of the original polymers by H-1- and C-13-n.m.r. It was found t hat the backbone chains of poly(macromonomer)s as well as the poly(3PB MA) chain had a syndiotactic triad in the range of 58-62%, but the cha ins still had a similar tactic structure comparable with those of poly (methacrylate)s having a short alkyl chain and the fractions of tactic triads obeyed the Bernoullian statistics. This fact indicates that th e specific multibranched structure around the propagating radicals as well as the ester polymer chain of the macromonomer does not have much effect on the chain tacticity, although the molecular conformation of the central backbone chain of the formed poly(macromonomer)s is stron gly affected by the polystyrene branch chains of high branch density, as described previously. (C) 1998 Elsevier Science Ltd. All rights res erved.