Methyl formate, from photodegradation

The fact that the decrease in molecular weight in the photodegradation of polymethylvinylketone does not continue at the same rate throughout the irradiation has been ascribed to the occurrence of a competing reaction that opposes the main chain scission process. This is assumed to be the formation of new polymer—polymer linkages by mutual recombination of macro-radicals resulting from the addition of CHj or CH3—CO to unsaturated chain ends formed in the Norrish type II reaction [55]. Evidence for the presence of such macro-radicals is found in the production of graft copolymers when solutions of polymethylvinylketone in various monomers (acrylonitrile, methyl methacrylate, vinyl acetate) are irradiated [57]. 

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