Theory of films. - II. The triple-layer film

The electrostatic and van der Waals forces and their coupling in aqueous systems with triple-layer geometry is considered. A general problem is formulated which includes the free-standing soap films, the swelling of clay plates and possibly the interaction between lipid membranes, as special cases. This problem is solved for the electrostatic repulsion and the zero-frequency contribution to the van der Waals attraction including the effects of fluctuating surface charges and the relaxation of the diffuse double layer.