Media effects on the kinetics of anthracene photo-oxidation in polymers

An improved quantitative analysis of the photochemical reaction of diphenylanthracene (DPA) in thin films of poly(ethyl methacrylate) (PEMA) is reported. This analysis confirms the previous suggestion (J.R. Sheats, J. Phys. Chem., 94 (1990) 7194) that the rate of reaction between singlet oxygen and DPA decreases as the reaction proceeds, consistent with the hypothesis that the free volume is decreased by endoperoxide formation. For DPA]≈30 wt.%, the rate constant decreases by approximately 50% for complete conversion. The initial value is 25-fold smaller than in fluid solution, and decreases slightly as DPA] is increased.