Abnormal Acceleration of the Rate of Bulk Polymerization of Styrene

Abstract The bulk polymerization of styrene initiated by 2,2′-azobisisobutyronitrile was carried out up to high conversion at 60°C. The comparison of the experimental conversions∼time data with calculated ones showed that there was a considerable deviation between them. The rate of the polymerization became explosively great toward the last. Assuming the combination termination, the cumulative degree of polymerization was calculated and the values were compared with those obtained experimentally. The deviation at high conversion might be owing to the decrease in the catalyst efficiency as suggested by Robertson. However, the assumption that the polymer molecules have been produced only by combination is very doubtful. The study of the molecular weight distribution suggested that the abnormal increase in the rate and the degree of polymerization seemed to be owing to the burying of the growing polymer radicals in themselves in the highly viscous solution.