A simple method for prediction of gas permeability of polymers from their molecular structure

Abstract

A method for the prediction of gas permeabilities (P) through polymers from their chemical structure has been developed on the basis of the ratio of molar free volume to molar cohesive energy, Vf/E. The permeation of small gas molecules through polymer membranes is dependent on the chain packing density measured by Vand segmental motion of polymer chains measured by E. But no simple relationship between P and Vf or E alone was found. The permeability data of more than 60 polymers covering 7 orders of magnitude for six gases have been treated with linear regression analysis. All plots of logP vs. Vf/E gave good straight lines. It is also found that a linear relationship holds when plotting both the intercepts and slopes of log P vs. Vf/Ecoh lines against square of the diameters of gas molecules. Therefore, the permeabilities of all the non-swelling gases through a great variety of polymers can be estimated using two correlations above. Moreover, this method is more accurate than others in the literature and may found useful for the selection of gas separation or barrier membrane materials. © 1991 The Society of Polymer Science, Japan. All Rights Reserved.