Luminescence studies in polymers—X: Triplet energy migration in copolymers styrene-vinylbenzophenone. Decay-time and its relation to phosphorescence emission and excitation spectra

Abstract

The decay of the phosphorescence of copolymers styrene-vinylbenzophenone excited with u.v. light of 365 nm either in glassy solution or as films at 77°K has been analysed. In glassy solution, the decay is exponential for a wide range of copolymer composition ( τ = 5·10 −3 sec). The decay of films reveals the presence of a second type of trap with a longer life-time ( τ = 2·10 −2 sec). The importance of these traps increases with the vinylbenzophenone content. The efficiency of triplet energy migration also increases with vinylbenzophenone content as a result of exchange interactions between benzophenone groups. The results are in agreement with Voltz's theory at moderate vinylbenzophenone content (<50 mole %).