Preparation and photolysis of poly‐p‐methoxyacrylophenone and its copolymers with styrene and methyl methacrylate

Poly‐p‐methoxyacrylophenone (PPMeOAP) and its copolymers with styrene (PMe‐OAP–S) and with methyl methacrylate (PMeOAP–MMA) were prepared. The photolysis in solution with 313 and 366 nm radiation was followed viscometrically. In solvents such as chlorobenzene and ethyl benzoate, random main‐chain scission from n–π* excited triplet state occurs. The lowest excited triplet state in formic acid and in ethylene chlorhydrin is of the character π–π*, from which no main‐chain scission occurs. In solvents in which destruction occurs, the main‐chain scission is retarded by triplet quenchers, such as naphthalene, 2,5‐dimethyl‐2,4‐hexadiene, and biphenyl. Quenching experiments indicate that the lifetime for the excited triplet state of PPMeOAP is 25 times that for polyacrylophenone. In PMeOAP–MMA copolymers, quantum yields of main‐chain scissions were lower and lifetimes of excited triplets were longer than in PPMeOAP, due to hindered intramolecular photoreaction.