Dependence of water sorption in polyimides on the internal linkage in the diamine component

The dependence of the water sorption behavior of polyimide thin films upon different diamine fragments was gravimetrically investigated. It was found that the diffusion coefficient and water uptake were strongly dependent upon the internal linkage in the diamine fragment, and varied in the range of 1.6x 10(-10) 13.5x10(-10) cm(2)/s and 1.52 similar to 5.63 wt.%, respectively. The water sorption behavior of the polyimide films decreased with increasing bulkiness of the internal linkages in the diamine fragments: BPDA-PDA < BPDA-Bz < BPDA-ODA < BPDA-DDS < BPDA-FDA. Specifically, BPDA-DDS and BPDA-FDA polyimide films with bulky internal linkages in the diamine fragments showed poor chain orientation and low intermolecular packing order, leading to relatively high water sorption (i.e. fast diffusion and high water uptake). (C) 2001 Published by Elsevier Science Ltd. All rights reserved.