Ionic Transport Behavior across Charged Membranes with Low Water Content. I. Theoretical Aspect of Membrane Potentials in Membranes Having Inhomogeneously Distributed Fixed-Charge Groups

This is our first report on the elucidation of the ionic transport phenomenon across charged membranes with low water content. In the present study, we proposed a new theoretical model of ionic transport across charged membranes with low water content, considering the effects of both an inhomogeneous fixed-charge distribution and the ion pairs in the membrane. We tried to analyze theoretically the properties of charged membranes (membrane potentials across charged membranes and the effective charge density of the charged membranes). Our theoretical prediction suggested that ion-pair formation was facilitated by the increase in the fixed-charge density of the membrane, the decrease in the dielectric constant of the membrane, and the increase in the valence of the counterion. It was also indicated that ion pairing depended on the center-to-center distance in an ion pair.