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The photolysis of copolymers of ethylene and carbon monoxide containing 1-9 mol % CO has been studied in solution and in the solid phase. Irradiation of the copolymer with light of wavelength 3130 A results in molecular weight degradation, evolution of carbon monoxide, and the formation of terminal vinyl groups. These effects are explained in terms of the well-known Norrish type I and type II reactions of ketones. The type II reaction, an intramolecular elimination, appears to be independent of temperature and phase and is not quenched by atmospheric oxygen. In the glass transition region, however, the type II reaction is inhibited, probably due to restriction of the freedom of internal motion of the polymer chain. The type I reaction produces free radicals and is temperature dependent. At 120°, the two processes make approximately equal contributions to a total quantum yield for reaction of about 0.05. However, at ambient temperature the type II process accounts for the major part of the chemical reaction.

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