Water-sorption behavior of p-phenylene diamine-based polyimide thin films

摘要

Four different p-PDA-based polyimide thin films were prepared from their respective poly(amic acid)s through thermal imidization at 400 degrees C: poly(p-phenylene pyromellitimide) (PMDA-PDA); poly(p-phenylene biphenyltetra carboximide) (BPDA-PDA); poly(p-phenylene 3,3',4,4'-oxydiphthalimide) (ODPA-PDA); and poly(p-phenylene 4,4'-hexafluoroisopropylidene diphthalimide) (6FDA-PDA). Water-sorption behaviors of polyimide films were gravimetrically investigated at 25 degrees C and 22-100% relative humidity by using the modified electromicrobalance (Thin Film Diffusion Analyzer). The diffusion coefficients of water for the polyimides varies in the range of 1.6 to 10.5 x 10(-10) cm(2)/s, and are in the increasing order: BPDA-PDA < PMDA-PDA similar to ODPA-PDA < 6FDA-PDA. The water uptakes of polyimides vary from 1.46 to 5.80 wt %, and are in the increasing order: BPDA-PDA < ODPA-PDA < 6FDA-PDA < PMDA PDA. The water-sorption behaviors for the p-PDA-based polyimides are closely related to the morphological structure; specifically, the diffusion coefficients in p-PDA-based polyimide thin films are closely related to the in-plane orientation and mean intermolecular distance, whereas the water uptakes are affected by the packing order. (C) 2000 John Wiley & Sons, Inc. [References: 32]