Singlet-Singlet, Triplet-Singlet, and Triplet-Triplet Energy Transfers. Evidence for Triplet Migration among Pendant Phenyl Groups of Polystyrene

Chemiluminescent techniques have been employed to investigate electronic energy transfer from ketone donors (acetone, acetophenone) to acceptors (e.g., 9,lO-diphenylanthracene and biphenyl) in films of polystyrene and polymethyl methacrylate at 50 "C. Tetramethyl-l,2-dioxetane and 3,4-diphenyl-3,4-dimethyldioxetane were used to generate excited (singlet and triplet) acetone and (triplet) acetophenone, respectively. Analysis of quenching data in terms of the Perrin, Forster, or Dexter models all yielded critical transfer radii, R,, in the range of 23-29 8, for singlet-singlet and for triplet-singlet energy transfer. For triplet-triplet energy transfer, the values of R, were in the range of 11-17 8, with the exception of the acetone triplet to 1,4-dibromonaphthalene transfer in polystyrene, for which R, = 21 8,. Evidence is presented which supports the postulate that triplet energy migration among the pendant phenyl groups on the polystyrene backbone may cause unexpectedly large R, values for triplet-triplet energy transfer.