Elimination Reaction of Phenyl Groups from Polystyrene in the Presence of Silica-Alumina Catalyst

Abstract

From the standpoint of synthesizing reactive polystyrene through functionalyzation, the reaction leading to the elimination of phenyl group from the main chain of polystyrene was investigated by the catalytic degradation of polystyrene in the presence of silica-alumina catalyst. In low temperature region (190-230°C), a remarkable decrease in molecular weight and the formation of benzene was detected. In particular, a high benzene yield in the early stage was noted. From the structural analysis of degraded polystyrene by NMR, it was found that the number of phenyl groups in the main chain sharply decreased. The amount of phenyl groups eliminated was approximately 2-3 moles per 10 monomer units at each temperature. Also, ethylene units were observed to be formed in the degraded polystyrene in the ratio of 3-18 mol%. These values are nearly the same as those for the eliminated phenyl groups under the same conditions. Therefore, as in the case of the copolymer of styrene-ethylene, modefied polystyrene possessing ethylene units in the main chain was synthesized by catalytic degradation in the presence of silica-alumina catalyst.