Absorption and Fluorescence Spectra and Thermal Properties of Novel Transparent Polyimides.

Ultraviolet-visible absorption spectra and fluorescence spectra of PI(6FDA/DCHM) and PI(6FDA/PDA) were investigated, as well as their thermal properties. Both PI(6FDA/DCHM) and PI(6FDA/PDA) showed high transparency in the visible region. Inter- and intra-molecular charge transfer were weakened by introducing fluorinated dianhydride, 6FDA, and/or alicyclic dicyclohexyldiamine, DCHM, in polyimide main chains. Excitation-wavelength dependence was found in the fluorescence spectra, which suggests inhomogeneous, less ordered aggregation in polyimide films including 6FDA or DCHM. Both PI(6FDA/DCHM) and PI(6FDA/PDA) had glass transition temperature, Tg of about 250°C from the TMA measurements, which proved that thermal stability of polyimides was not reduced by introducing the alicyclic group.