Relationship between polymer structure and gas transport properties in a series of fluorine-containing aromatic polyamide membranes for oxygen enrichment

Abstract

In this work, a series of fluorine-containing aromatic polyamide membranes were prepared by direct polycondensation of 4,4′-hexafluoroisopropylidene-dibenzoic acid with various aromatic diamines, and the associated gas transport and sorption properties were investigated. The properties of the prepared aromatic polyamides were examined by elemental analysis, FTIR, and X-ray diffraction. It was found that both gas diffusivity and permeability can be increased by the introduction of bulky substituted groups and arylene ether groups into the polymer backbone. Membranes with oxygen permeability of 3.8 barrers and O 2/N 2 selectivity of 4.6 were obtained by using the polyamide with 2,5 di- tert-butylbenzene group in the polymer backbone. It was also found that the relationship between the membrane structure and the sorption properties can be well explained by the dual sorption model.