Retardation of the anaerobic photo-degradation of poly(4′-methoxyacrylophenone)

Abstract

The effects of the UV absorbers Tinuvins 327 and 900 on the anaerobic photo-degradation of poly (4′methoxyacrylophenone) have been investigated, the stabilizers being added to thin films and to dilute solutions (in CH 2Cl 2) of the polymer. The photochemistry was investigated from two points of view, i.e. random chain scission and the formation of long-wave chromophores. Both Tinuvins retard these, the principal photo-reactions. However, neither acts simply as a UV absorber, despite the coincidence of their long-wave UV absorptions with that of the polymer. In the case of chain scission, it was established that both Tinuvins also acted as triplet quenchers, in accordance with Stern–Volmer Kinetics and quenching rate constants had values typical of those observed for diffusion controlled quenching. The situation with regard to chromophore formation was more complex, and could not be interpreted in terms of large scale quenching. However, the complexity of the solid state system, and the inherent lack of mobility of the small molecules within the polymer at sub- T G temperature, would reduce the effectiveness of any quenching process. No convincing evidence was obtained for radical scavenging by the Tinuvins.