Water sorption behaviors of the BPDA-based polyimide films depending upon the structural isomers of diamine

For the biphenyltetracarboxylic dianhydride (BPDA)-based polyimide thin fil ms, the water sorption behaviors were gravimetrically investigated by using a thin film diffusion analyzer. The water sorption behaviors of the polyim ide thin films are quite different and strongly dependent upon the sort of polyimide. The diffusion coefficients of the polyimide thin films vary in t he range of 1.6 x 10(-10) to 12.4 x 10 (10)cm(2)/s and the water uptakes va ry from 1.52 to 5.25 wt %;. Both the diffusion coefficient and water uptake of the polyimide thin films are in the increasing order: BPDA-pPDA < BPDA- p,p'ODA < BPDA-p,m'ODA < BPDA-mPDA <similar to> BPDA-p,p'DDS < BPDA-m,m'DDS . Specifically, the polyimide films with para-oriented linkages in backbone structure showed relatively lower diffusion coefficient and water uptake t han the corresponding polyimide films with meta-oriented linkages because o f the well developed crystalline structure and good intermolecular chain or dering. In addition, the polyimide thin films having higher chain order sho wed relatively lower diffusion coefficient and water uptake. The crystallin ity and intermolecular chain ordering in the morphological structure are cr itical parameters in controlling the water sorption behaviors of the polyim ide thin films. (C) 2001 John Wiley & Sons, Inc.