Photodegradation of chloromethyl vinyl ketone polymer and copolymers with styrene and α-methylstyrene

The photodegradation behaviour of chloromethyl vinyl ketone (CMVK) polymer has been compared with that of polymers of methyl and tertiary butyl vinyl ketones, MVK and t-BVK, respectively. The results obtained for poly(CMVK) showed that the quantum yields of main chain scission in dioxane and of the Norrish type I reaction (ø_I) in film were 0.18 and 0.61 times, respectively, greater than those of poly(MVK), while ø_I for poly(t-BVK) was about 19 times that of poly(MVK). It was also found that the photolysis of poly(CMVK) produced a considerable amount of hydrogen chloride and its quantum yield ø_HCl was higher than ø_I, i.e.$\text{ø}{}_{\mathrm{<mtext>HCl</mtext>}}\text{ø}{}_{\mathrm{<mtext>I</mtext>}}\text{= 1.7}$. This was attributed to the intramolecular transfer of photoexcited energy from the ketone chromophore to the adjacent chloromethyl group. The existence of such a reaction was supported from the remarkable acceleration of the photopolymerization of methyl methacrylate. The photodegradation mechanism of poly(CMVK) is discussed, in the light of the results obtained above and from the studies on quenching and on the photodegradation of CMVK copolymer.