Catalytic degradation of polystyrene in the presence of aluminum chloride catalyst

The authors have been engaged in studies on the bulk catalytic degradation of various polymers in the presence of solid catalysts. This paper reports the results of bulk degradation of polystyrene in the presence of aluminum chloride carried out at 50°C for 1 to 4 h. The only volatile degradation product was benzene over the entire course of reaction. The molecular weight of the polymer decreased linearly with reaction time down to Mn = 5·3 × 10 3 (after 4 h). A linear relationship was also observed between the decrease in molecular weight and the decrease in the content of phenyl groups. Stepwise changes in polymer structure were found to take place, which were ascribed to the formation of the indane skeleton in the main chain. Based on these results, combined with the result of an experiment using a model compound (1,3,5-triphenylhexane), a reaction mechanism was proposed which postulates (1) elimination of phenyl groups induced by the addition of protons (initiation step), (2) decomposition of the resulting polymeric carbonium ions through β-scission accompanied by a drop in molecular weight and (3) change in polymer main chain structure, reactions (2) and (3) proceeding competitively.