Photodecomposition of polystyrene on long‐wave ultraviolet irradiation: A possible mechanism of initiation of photooxidation

The long‐wave (λ < 3000 Å) photo‐oxidation of polystyrene in solution at 25°C has been studied osmometrically. Two types of chain scission have been observed: a purely photo process which occurs completely independently of oxygen and which is attributed to fission of photolabile groups in the polymer, and another process associated with random photolyses of the products of oxidation Scavenger experiments with 131I2 have shown that approximately two iodine atoms are incorporated per chain scission when photolysis is carried out in solution (benzene, hexafluorobenzene, methylene chloride) under high vacuum conditions in the presence of 131I2. No iodine incorporation or chain scission occurs when ionically prepared polystyrenes are treated similarly. The nature of the photolabile bond has been discussed, and there is some evidence for a peroxidic linkage arising from oxygen copolymerization in the chains. It is suggested that fission of the photolabile groups contributes to the initiation of the long‐wave photooxidation of the polymer.