Thermal degradation of poly( o-propionylstyrene)

The thermal degradation of poly( o-propionylstyrene) (POPS) was studied at 385°C under high vacuum. The principal reactions are removal and decomposition of the propionyl substituents, depolymerization, oligomer formation and chain scission. While the mechanism of degradation is qualitatively similar to that of poly(styrene), the probability of transfer reactions occurring with the polymer is considerably greater, on account of the presence of ethyl and methyl radicals (derived from the propionyl groups). The resulting macroradicals undergo β-scission, and this reaction accounts for most of the chain scission (yielding a terminally unsaturated molecule and another macroradical). These two species further decompose to give (respectively) oligomeric products and monomer, the relative abundance of oligomers to monomer being about twice that observed for PS, and this has been attributed to shorter zip lengths for depolymerization and to the more likely occurrence of transfer reactions in POPS.