The tacticity of the backbone chain of poly(macromonomer)s of ω-methacryloyloxyethyl polystyrene macromonomers prepared by radical chain polymerization

Abstract

The effect of the polystyrene chain as a bulky long ester group of methacrylate monomer on the chain tacticity was investigated in the radical chain polymerization of ω-methacryloyloxyethyl polystyrene macromonomers of different molecular weights. The macromonomers and 3-phenylbutyl methacrylate (3PBMA), which corresponds to the unimer model of the macromonomer, were synthesized and polymerized with azobisisobutylonitrile in benzene at 60°C. The polymers obtained were converted to poly(methyl methacrylate)s by acid hydrolysis reaction followed by methyl esterification with diazomethane to estimate the chain tacticity of the original polymers by 1H- and 13C-n.m.r. It was found that the backbone chains of poly(macromonomer)s as well as the poly(3PBMA) chain had a syndiotactic triad in the range of 58–62%, but the chains 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 Bemoullian statistics. This fact indicates that the 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 strongly affected by the polystyrene branch chains of high branch density, as described previously.