Gas separation properties of siloxane/polydimethylsiloxane hybrid membrane containing fluorine

Abstract

A cross-linking agent containing silicon–hydrogen bond and trimethoxylsilicon groups was synthesized by silicon–hydrogen addition reaction. Based on a convenient and mild sol–gel process as well as cross-linking reaction, a siloxane/polydimethylsiloxane (PDMS) hybrid membrane containing fluorinated side-chains was also prepared by using 13-fluorinated triethoxysilane and PDMS containing vinyl group as matrix materials. The chemical structure, microstructure and mechanical property of the hybrid membrane were characterized. The effects of gas pressure difference, temperature and fluorine content on permselectivity of the hybrid membrane were investigated. The results showed that the membrane had better membrane-forming and high permeability as well as selectivity than normal PDMS membranes. The oxygen permeability coefficient was 602 Barrer and oxygen/nitrogen separation factor was up to 3.47. The permeation properties of the hybrid membrane fluorinated are higher obviously than those of Robeson's upper bound and of unfluorinated PDMS membrane. Both a high permeability and a high selectivity of the hybrid membrane may be attributed to the introduction of fluorine atom into PDMS membrane, cross-linking network of molecule structure and mild sol–gel process.