The Hamaker and the Lifshitz approaches for the Van der Waals interaction between particles of composite materials dispersed in a medium

Based on the superpositional principle of the classical Hamaker–De Boer approach to the Van der Waals interaction, an equation for the interaction energy between two identical composite particles in a medium has been developed. The particles are supposed to be composed of an arbitrary number of components that are intimately mixed to avoid appreciable scattering of interacting EM waves. A discussion is presented on how intimately the components have to be mixed for the theory to be applicable. As an example, the main theoretical result is applied to porous polystyrene particles in water, while the pores are not filled with water (‘non-wetting surface’). Numerical results for composite particles are evaluated, using interaction parameters as obtained by various methods that are based on either the Hamaker–de Boer or the Lifshitz approach.