Energy transfer in polymers—VII: Triplet energy migration and transfer in copolymers styrene-vinylbenzophenone

Abstract

The efficiency of triplet energy transfer from the benzophenone group to naphthalene has been studied in a series of copolymers styrene-vinylbenzophenone, either as films or in glassy solutions at 77 K. Energy migration has been shown to be efficient in both cases. For a given copolymer, Hirayama's critical distance is larger in films than in glassy solutions. In both cases, it decreases with decreasing vinylbenzophenone content. The number of jumps between identical molecules during the life-time of the excited state has been calculated according to the hopping model and Voltz theory on energy migration. The results show that energy migration in these solid polymers is not the consequence of exchange interactions decreasing exponentially with the mean distance between the chromophores. Organized regions, characterized by a higher efficiency of transfer, have to be taken into account.