FTIR-ATR studies of the sorption and diffusion of acetone:water mixtures in poly(vinyl alcohol)-clay nanocomposites

Abstract

The simultaneous ingress of acetone and water into dried PVOH-clay nanocomposites containing 2.5 wt% or 5 wt% of well dispersed Na-Cloisite, using FTIR-ATR, has been compared with that into pure PVOH films. The rate at which water and acetone moved through the PVOH films is significantly reduced (i) at high acetone concentrations and (ii) when clay is incorporated in the PVOH film. For example, it takes 9 min and 17 min for water and acetone, respectively, to saturate a 25 ± 5 μm PVOH film containing 2.5 wt% of well dispersed clay when the acetone:water ratio is 90:10 v/v compared with ca. 1 min for a pure PVOH film when the acetone:water ratio is 70:30 v/v. The presence of significant quantities of water in the PVOH (nanocomposite) films was necessary before acetone began to permeate the film. The acetone entering the evanescent field was always highly hydrated even if the water content of the reservoir in contact with the film was low. There was no substantial evidence that the presence of clay altered the way in which the PVOH interacted with the acetone:water mixtures. The clay only acted to increase the tortuosity of the path through the film to the ATR prism.