Water Transport in Poly(n-butyl acrylate) Ion-Selective Membranes

Water transport across poly(n-butyl acrylate) membranes is a critical process in the mechanism of operation for the ion-selective layers used in the construction of electrodes that detect ionic species. We report the results from a hologram-membrane composite which was used to characterize the rate of water transport through the ion-selective membrane. A diffusion coefficient, Dapp approximate to 10(-6) cm(2) s(-1) was estimated from holographic data and confirmed by FTIR data. An osmotic pressure driven mechanism was rejected and Case II diffusion of water vapor was indicated, suggesting low condensation within the membrane itself. FTIR spectroscopy was also used to characterize the water species at an interface with the membrane revealing composition-dependent water transport equilibria.