Theoretical study on the mechanism of coloration of polyimides

Abstract

The mechanism of coloration of polyimides has been investigated theoretically and experimentally. Since light is considered to be absorbed by polyimides via the charge transfer excitation, we used the long-range-corrected time-dependent density functional theory recently developed by Tsuneda et al [J. Chem. Phys. 2004, 120, 8425] for the calculation of excitation energies and oscillator strengthes. Classical molecular dynamics simulations for packed chain models of polyimides were also performed to analyze the structural information of polyimides in condensed phase. In order to predict the transparency of polyimides film, we developed the theoretical method by combining the result of electronic structure calculation and that of molecular dynamics simulation. We compared our theoretical results with experimental ones and discussed the difference between them. As a result, we could clarify the new mechanism of coloration and obtain the reasonable results for the theoretical UV-visible spectra.