ATR-FTIR spectroscopic studies of the structure and permeability of sulfonated poly(ether sulfone) membranes. Part 2.—Water diffusion processes

Abstract

Attenuated total reflection (ATR) FTIR spectroscopy has been used to study the diffusion of water into sulfonated poly(ether sulfone) films as a function of film thickness, preparation solvent and degree of sulfonation. Dual mode diffusion is found in all cases with diffusion coefficients D₁ and D₂ and weighting factor x₁ which vary depending on the conditions. Variations with film thickness are thought to be due to the way in which information is weighted towards the D₁ and D₂ modes. Changes in D with preparation solvent are due to the degree of ion solvation, cluster formation and subsequent ability to interact with water. Changes in D with degree of sulfonation are easily attributed to interfacial activity of water and therefore the greater the weighting of the D₁ mode at higher SO₃^– level.