Energy transfer processes can, in principlc, represent a powerful new mechanism for thc stabilization of polymers against degradation by ultra-violet light. The mechanism involves thc transfer of electronic excitation from an absorbing group in the polymer to a 'quenching' group by eithcr an intraor intermolecular process. The efficiency of such processes depends in a complex way on the nature of the cxcited states of thc donor and acceptor groups, and on the mobility of the polymer chain in

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... solid state. Sturlies are reported on the quenching of the photodcgradation of polymers containing kctone and aromatic groups by various stabilizers.