APPROXIMATE ANALYTICAL EXPRESSIONS FOR THE PROPERTIES OF A DOUBLE-LAYER WITH ASYMMETRIC ELECTROLYTES - ION-PENETRABLE CHARGED MEMBRANES

The Poisson equation describing the electrostatic potential distributi on for a planar geometry with asymmetric electrolytes in the liquid ph ase is analyzed. In particular, an ion-penetrable charged membrane is considered. Typical examples in practice include biological cells and some artificial membranes. An approximate analytical solution to the n onlinear Poisson equation is derived, and explicit expressions for the properties of the double layer including surface excess of co-ions, H elmholtz free energy, and entropy are presented. The results of numeri cal simulation reveal that the present approximate results provide rea sonably accurate estimations for both the electrostatic potential dist ribution and the relevant thermodynamic properties of the system under consideration. (C) 1994 Academic Press. Inc.