Interpretation of d-spacing determined by wide angle X-ray scattering in 6FDA-based polyimide by molecular modeling

Interpretation of d-spacing determined by wide angle X-ray scattering (WAXS ) is of great interest in the study of gas diffusivity or permeability in g lassy polymers. Studies of WAXS analysis and of molecular modeling were car ried out as a new approach in which to interpret the d-spacings in polyimid e synthesized from 2,2-bis (3,4-carboxyphenyl) hexafluoropropane dianhydrid e (6FDA). The tetramer conformation and the amorphous polymer structure at 25 degrees C were modeled using the semi-empirical molecular orbital method and the molecular dynamics method. The corresponding theoretical X-ray sca ttering functions were calculated from the atomic coordinates using Debye's equation and then compared with the experimental data. The amorphous polym er model was found to be superior to the tetramer conformation model in the predicting experimental X-ray scattering function. It was found that the d -spacing for 6FDA-BAAF polyimide was clearly affected by intramolecular dis tances containing F atoms. (C)2000 Elsevier Science B.V. All rights reserve d.