The use of FTi.r.-a.t.r. spectroscopy to characterize penetrant diffusion in polymers

Abstract

The diffusion of small molecules in polymers was measured using Fourier transform infra-red-attenuated total reflection (FTi.r.-a.t.r) spectroscopy, a new approach which allows one to study liquid diffusion in thin polymer films in situ. The system used to test this technique was the diffusion of liquid water in polyacrylonitrile (PAN). The diffusion coefficients that were measured were in good agreement with those reported in the literature for high-activity water vapour in PAN. The test also demonstrated both the reproducibility and accuracy of FTi.r.-a.t.r. experiments for measuring the diffusion coefficient. The diffusion coefficient and the amount of water sorbed at equilibrium appear to be dependent on the temperature at which the films were treated. The method described here shows great potential for elucidating penetrant-penetrant and penetrant-polymer interactions during the diffusion process owing to the spectroscopic nature of the technique.