GENERATION OF NONRANDOM CHROMOPHORE DISTRIBUTIONS BY THE PHOTO-FRIES REACTION OF 2-NAPHTHYL ACETATE IN POLY(METHYL METHACRYLATE)

The photochemical Fries reaction of 0.1-0.2 M 2-naphthyl acetate in glassy poly(methyl methacrylate) converts the naphthalene compound into products that act as long-range quenchers. Because each quencher suppresses formation of additional photoproducts in its immediate vicinity, the result is the formation of a nonrandom distribution of reactant donors and photoproduct quenchers, in which chromophores are more evenly distributed than in a truly random distribution. Singlet electronic energy migration and transfer within these nonrandom chromophore distributions were studied by steady-state fluorescence spectroscopy and fluorescence decay measurements. The donor fluorescence decays obtained for nonrandom distributions are clearly different from those predicted by models based on random chromophore distributions. Non- random distributions are converted to random distributions by solvent treatment or annealing for 4 days or more. The donor fluorescence decays of these new chromophore distributions correspond within experimental error to the predictions of the Förster and Loring-Andersen-Fayer models for energy trapping in random distributions. © 1990, American Chemical Society. All rights reserved.