(330n) Anomalous Diffusion of Water Vapor in Dense Polyimide Membranes Prepared from 3,3'4,4'-Benzophenonetetracarboxylic Dianhydride and Phenylene Diamine

The dynamic sorption and diffusion of small solvent molecules in dense polymeric membrane are the prerequisite for membrane separation processes such as pervaporation, vapor permeation and gas separation. In this study, the dense polyimide membrane was prepared form 3,3'4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and phenylenediamine (PDA) monomers. The dynamic sorption and diffusion behaviors at 298 K and 308 K of water vapor in BTDA + PDA polyimide membrane were investigated by experiments. According to the results, the diffusion behaviors did not obey the Fickian diffusion law and belonged to anomalous diffusion. The anomalous diffusion factors, calculated from the fractal diffusion theory, of water vapor in BTDA + PDA polyimide membrane are 2.38 at 298 K, and 2.26 at 308 K. It implies that the diffusion of water vapor in BTDA + PDA is more slowly than the Fickian diffusion.