On the kinetics of propylene polymerization

The kinetics of propylene polymerization catalyzed by a commercial sample of highly activated titanium trichloride and diethylaluminum chloride have been investigated. Polymerizations were carried out at various temperatures, pressures, and catalyst concentrations, and reaction rates were determined by a gasometric technique. The concentration of metal—polymer bonds was measured by quenching aliquots of the reaction mixture with methanol‐O‐t and radioassaying the polymer. The rates were found to decrease with time while the concentration of metal—polymer bonds increased. These results were interpreted in terms of two exchange reactions of the active sites, one which leads to an inactive site, and another which produces a different active site. With the aid of a kinetic model based on this mechanism, number‐average and weight‐average molecular weights were calculated and were compared with values obtained from fractionation, osmometry, and viscometry.