The laser-pulse-excited phosphorescence of benzophenone molecularly dispersed in poly(methyl methacrylate) (PMMA), poly(isopropyl methacrylate) (PIPMÁ), and poly(methyl acrylate) (PMA) decays nonexponentially for the temperature range ß< T < Tg, while it decays single-exponentially for both T < ß and T > Tg of each polymer. The kinetics for the nonexponential decay of benzophenone triplet in these polymer matrices at 80-433 K are given by using the diffusion-controlled rate coefficient with a time-dependent transition term for the dynamic quenching process of benzophenone triplet by side-chain ester groups of the matrix polymers. The resulting kinetic parameters, namely the reciprocal lifetime (l/ ), a factor characteristic of the deviation from single-exponential decay (C), and the diffusion coefficient of interacting groups (D), reflect molecular motion at the glass transition (Tg) and other secondary transitions (Ta. and ß) of the matrix polymers.

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ABSTRACT:Decay curves and lifetimes of benzophenone phosphorescence in polystyrene and in bisphenol A polycarbonate (BPA-PC) at 80----433 K significantly reflect change in the molecular motion of matrix polymers such as glass transition, /3-transition, and }'-transition. The non-singleexponential decay. curves were observed in both polymers at temperatures between T, and T., and analyzed using the diffusion-controlled rate coefficient with a time dependent transient term for the dynamic quenching process of benzophenone triplet by phenyl or phenylene groups in the matrix polymers. The diffusion coefficients, D, of the reacting functional groups in polystyrene and BPA-PC for the wide temperature range below T. are much larger than that in PMMA in the same temperature range, showing a higher quenching ability of these polymers for the benzophenone triplet.