Electrical double-layer interaction between two eccentric spherical surfaces

Abstract

The nonlinear Poisson—Boltzmann equation has been solved numerically for a model system in which a spherical colloid is placed eccentrically in the core of a spherical shell of colloidal dimension. The proposed model simulates systems such as colloidal particles entrapped in near-spherical cavities in porous media, colloidal particles in concentrated suspensions, macromolecules (e.g., proteins) solubilized in reverse micelles, and drug particles encapsulated within liposomes in drug delivery systems. To describe the electrical double-layer interaction in the above systems of interest, the interaction energy has been calculated by first solving numerically the Poisson—Boltzmann equation for the model system, as well as for each of its component surfaces (the surface of the shell and the outer surface of the particle in the core). The equation has been solved in bispherical coordinates for the model system. Both constant surface potential and constant surface charge types of boundary conditions have been treated. The effects of electrical double-layer interaction on the aforementioned systems have been predicted based on the results of interaction energy calculations.