Photophysical Processes in Aromatic Polyimides. 2. Photoreduction of Benzophenone-Containing Polyimide Model Compounds

Article abstract of DOI:10.1021/j100093a017

The photochemical kinetic parameters for the model compounds of benzophenone-containing polyimide were determined on the basis of the Stern-Volmer analysis.The quantum yield for the photoreduction, Φ_M, in dichloromethane decreased with an increase in the intramolecular charge-transfer (CT) caracter which depends upon the chemical structure of the amine components and the conformation around N-aryl group linkage.This could be explained well by a schematic photophysical mechanism in which the intersystem crossing followed by the hydrogen abstraction competes with the intramolecular CT process followed by effective deactivation.The phosphorescence spectra and lifetime at 77 K and the transient T₁ -> T_n absorption and emission spectra of the model compounds at 20 deg C suggested that T₁ is of pure (n,?*) state independent of the intramolecular CT character.It was found that benzophenonebisimides have the hydrogen abstraction rate constants no less than that of benzophenone (BP).