Curvature effects on electric double-layer forces Part 2.—Dependence of forces on cavity radius and the relative permittivity

Abstract

The effect of bulk relative permittivity on the swelling pressure inside spherical cavities and cylindrical pores is investigated using the Poisson–Boltzmann equation. It is found that at constant surface charge density, the swelling pressure decreases with increasing relative permittivity, opposite to the trend between two parallel plates. The relative permittivity also plays a special role in a force decomposition which leads to a reformulation of the double-layer force for different geometries as weighted averages of the hydrostatic pressures.