"Analysis of factors influencing preparation of high molecular weight polyisobutylene"

Isobutylene polymerization was studied with the rare-earth metal scandium cationic complexes as catalysts and molecular weight and its distribution, and glass transition temperature of polyisobutylene were investigated by screening the catalyst system, adjusting the ratio of monomer to catalyst and regulating the reaction temperature and time. The results showed that the constrained-geometry-configuration scandium dialkyl catalyst which had relatively smaller steric hindrance had the highest catalytic activity for isobutylene polymerization among 5 kinds of rare-earth metal scandium cationic catalysts. The higher mole ratio of monomer isobutylene to catalyst was, the higher number-average relative molecular weight the resulting polymer had. The lower reaction temperature was, the higher numbe-average relative molecular weight of the polymer was, however, when the reaction temperature was below -60 ℃, the number-average relative molecular weight of the polymer decreased significantly. The reaction time had little effect on the change of the number-average relative molecular weight of the polymer. In addition, the polymerization reaction temperature and time had no significant effect on the glass transition temperature of polyisobutylene.