Gas separation properties of PMDA/ODA polyimide membranes filling with polymeric nanoparticles

The success in synthesizing a variety of nanostructured materials in recent years have provided a new degree of freedom for the development of advanced polymer materials for gas separation. In this paper, a series of pyromellitic dianhydride (PMDA)/oxydianiline (ODA) polyimide (PI) membranes filling with polystyrene (PS) and poly(styrene-co-4-vinylpyridine) (PSVP)-nanoparticles were fabricated and their gas, separation properties for CO2, O-2, N-2 and CH4 were measured. Concerning the PI/PS-nanoparticle composite membranes. the gas permeabilities and selectivities decrease with the increase of PS-nanoparticles in the membranes. These are due to the increase in gas diffusion coefficients and the decrease in diffusion selectivities. For PI/PSVP-nanoparticle composite membranes, both increase in gas permeabilities and selectivities are observed when the PSVP-nanoparticles increase from 10 to 20 wt.% in the membranes, while both the diffusion coefficients and diffusion selectivities show decrease. It was found that the membrane containing 20% PSVP-nanoparticles shows both high gas permeability and high permselectivity towards CO2. These results may be ascribed to the high solubility of CO2 and O-2 in the pyridine-containing polymers and the relative homogenous distribution of PSVP-nanoparticle in the PI matrix. X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) were used to characterize the structure of the nanoparticles and the composite membranes. Temperature effects on the gas permeabilities and diffusivities of the membranes were studied. (C) 2002 Elsevier Science B.V. All rights reserved.