Polymeric photosensitizers: effects of intramolecular energy migration on sensitization efficiences
The occurrence of intramolecular energy migration was found to have no significant effect on the efficiency of ketyl radical formation via hydrogen abstration from cumene by benzophenone (BP) or poly(vinylbenzophenone) (PVBP). Rate constants were found to be 1.1 x 10/sup 6/ and 0.81 x 10/sup 6/ M/sup -1/ s/sup -1/ for the small molecule and the polymer, respectively. The large difference in rate constants, 9.6 x 10/sup 6/ and 22.2 x 10/sup 6/ M/sup -1/ s/sup -1/ for BP and PVBP, respectively, when tetrahydrofuran was used as a quencher is probably attributable to preferential solvation. Conversely, intramolecular energy migration was found to significantly enhance the overall efficiency of triplet energy transfer to 1-methylnaphthalene (MeN). Rate constants for formation of /sup 3/MeN were found to be 0.94 x 10/sup 9/ and 1.85 x 10/sup 9/ M/sup -1/ s/sup -1/ for BP and PVBP, respectively. An energy migration coefficient, LAMBDA, of 3.28 x 10/sup -5/ cm/sup 2/ s/sup -1/ and a frequency of energy migration, omega, of 7.88 x 10/sup 10/ x/sup -1/ were calculated for PVBP. For a series of copolymers of methyl methacrylate with vinylbenzophenone, values of LAMBDA and omega were strongly dependent on the ketone content of the polymer and decreased sharply at 40 mol % VBP or less.
- Research Organization:
- Univ. of Notre Dame, IN
- OSTI ID:
- 7169784
- Journal Information:
- Macromolecules; (United States), Vol. 17:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
METHYLNAPHTHALENES
PHOTOSENSITIVITY
POLYMERS
ENERGY TRANSFER
ABSORPTION SPECTRA
BENZOPYRENE
CUMENE
TETRAHYDROFURAN
ALKYLATED AROMATICS
AROMATICS
CONDENSED AROMATICS
FURANS
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
SENSITIVITY
SPECTRA
400500* - Photochemistry