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

The Poisson equation describing the electrostatic potential distribution for a planar geometry with asymmetric electrolytes in the liquid phase 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 nonlinear Poisson equation is derived, and explicit expressions for the properties of the double layer including surface excess of co-ions, Helmholtz free energy, and entropy are presented. The results of numerical simulation reveal that the present approximate results provide reasonably accurate estimations for both the electrostatic potential distribution and the relevant thermodynamic properties of the system under consideration. (C) 1994 Academic Press. Inc.