Abstract
AbstractThe stereoregularity of polystyrenes (PS's) obtained by γ‐ray and UV light irradiation was determined by 13C NMR spectroscopy, and the mechanism of polymerization was discussed. PS's obtained by 60Co γ‐ray irradiation in bulk, methylene chloride and carbon tetrachloride at 0°C showed bimodal molecular weight distributions. The stereoregularity expressed by the fraction of racemic dyads in the high molecular weight portions and the low molecular weight ones separated by thin layer chromatography (TLC) was 66 – 67% and 71%, respectively. The results indicate that the former portions are formed by a cationic mechanism and the latter by a radical mechanism. It was also confirmed that the polymerization by UV light irradiation with pyromellitic dianhydride (1,2:4,5‐benzenetetracarboxylic dianhydride) as an electron acceptor propagates by a cationic mechanism in polar solvents and by a radical mechanism in the bulk.
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