Photolysis of poly(p-isopropyl styrene)

The photodegradation of films of poly(p-isopropyl styrene) with 254 nm radiation at 10^?6mbar and 25±1° has been studied. The principal product is hydrogen but smaller quantities of methane and ethane and a trace of propane are also formed, indicating that the p-substituent also undergoes decomposition. Ultraviolet spectra show rapid changes, particularly in the 230–240 nm region, and a long wave absorption system extending into the visible region also appears. Solubility data indicate the simultaneous occurrence of cross-linking and chain scission, rates of both processes being significantly greater than those for poly(styrene); these results are explicable in terms of the inductive (+I) stabilization (due to the p-C₃H₇ group) of radicals formed on chain scission and of the participation of the p-C₃H₇ group in addition reactions. Quantum yields for the evolution of the gaseous products have been estimated.