M. Hasegawa et al., PHOTOPHYSICAL PROCESSES IN AROMATIC POLYIMIDES .2. PHOTOREDUCTION OF BENZOPHENONE-CONTAINING POLYIMIDE MODEL COMPOUNDS, Journal of physical chemistry, 98(42), 1994, pp. 10771-10778
The photochemical kinetic parameters for the model compounds of benzop
henone-containing polyimide were determined on the basis of the Stern-
Volmer analysis. The quantum yield for photoreduction, Phi(M), in dich
loromethane decreased with an increase in the intramolecular charge-tr
ansfer (CT) character which depends upon the chemical structure of the
amine components and the conformation around N-aryl group linkage. Th
is could be explained well by a schematic photophysical mechanism in w
hich the intersystem crossing followed by the hydrogen abstraction com
petes with the intramolecular CT process followed by effective deactiv
ation. The phosphorescence spectra and lifetime at 77 K and the transi
ent T-1 --> T-n absorption and emission spectra of the model compounds
at 20 degrees C suggested that T-1 is of pure (n,pi) state independe
nt of the intramolecular CT character. It was found that benzophenoneb
isimides have the hydrogen abstraction rate constants no less than tha
t of benzophenone (BP).