Stabilization of reactive species in polymethyl methacrylate

Abstract

A transient with absorption peaks at 1.645 and 1.88 µ^–1 has been observed when benzophenone solutions in polymethyl methacrylate (PMMA) were flashed with a xenon flash lamp. The decay time of this transient at 100, 220 and 293°K was the same as the decay time of phosphorescence at the same temperatures. Comparison of the transient absorption spectrum with the ketyl radical spectrum in ethylene glycol, suggests that the transient is not the ketyl radical but the triplet state of benzophenone. The effect of temperature on the lifetime and quantum efficiency of phosphorescence has been measured in order to determine the rate constants of radiationless transitions from the benzophenone triplet.