【Original Contribution】 Physical and Gas Transport Properties of Polyimide-Silica Hybrid Membranes treated with CO₂ gas

Abstract

The physical and gas transport properties of hyperbranched polyimide (HBPI)-silica hybrid membranes treated with carbon dioxide (CO 2 ) gas were investigated and compared with those of linear-type polyimide-silica hybrid membranes to estimate the influence of the molecular structure and hybridization on the stability of gas transport property. For all of the membranes examined, there was no marked change in the FT/IR spectrum or the UV-VIS spectrum before and after CO 2 treatment, indicating no influence on the polyimide molecular chain and the threedimensional Si-O-Si network themselves by the CO 2 treatment. In HBPI-silica hybrid membranes, it was suggested that CO 2 treatment did not cause deterioration of stability of gas transport property. The reason for this was that the restraints of the micro-Brownian motion or the densification of polyimide molecular chains and the stiffening of the three dimensional silica networks have been induced. In contrast, mild plasticization seems to have been caused in 6FDA-based linear-type polyimide-silica hybrid membranes. In addition, although CO 2 treatment decreased both the gas permeability and the selectivity of non-6FDA-based polyimide membranes, it increased the selectivity of the 6FDA-based polyimide membranes.