Synthesis of polyimides with aliphatic moieties and their charge transfer structure and photophysical processes

Abstract

Photophysical processes of polyimides with biphenyl moieties were investigated. Intra- and intermolecular charge transfer absorptions were calculated by subtracting absorptions of partially aliphatic polyimides from a fully aromatic polyimide. The absorptions due to the intra- and inter-molecular charge transfer are observed around 400nm, which is the origin of the color of polyimides. Charge transferred fluorescence with large Storks shift was for aromatic polyimides, while fluorescence from a local excited state was observed for a partially aliphatic polyimide. T-T absorption of the model compound was observed at 460nm with lifetime of 20μs, suggesting that the triplet state may be of locally excited, which is explained by the π-π* of the S1 state.