Structural changes in an aromatic polyimide on annealing at high temperatures and electron irradiation

The fine structure and molecular aggregation in the partially oriented state of an aromatic polymer, polyimide(PI) were investigated by means of wide-angle x-ray scattering(WAXS) and small-angle x-ray scattering(SAXS). By applying the Hosemann's analysis to the line broadenings in the WAXS, it was found that the length of the x-ray coherence region is about 80 A and that its value remains constant on annealing at high temperatures and/or electron irradiation. It was also shown on annealing that the second kind of distortion, the so-called g-factor decreases from 3.7 ∼ 4.0 % of the as-drawn PI to 2.0 ∼ 2.5 % but holds its value on electron irradiation. The SAXS curves show that after annealing at high temperatures the molecular aggregation in the as-drawn PI is of a two phase structure, composed of the high and low density regions. On the other hand, molecular aggregation in the as-drawn PI has not been clearly clarified in terms of the SAXS measurement. (author)