Microscopic theory of solvent-mediated long-range forces: Influence of wetting

¹ H. H. Wills Physics Laboratory, University of Bristol - Bristol BS8 1TL, UK
² Max-Planck Institut für Metallforschung - Heisenbergstr. 1, 70569 Stuttgart, Germany
³ ITAP, Universität Stuttgart - Pfaffenwaldring 57, 70569 Stuttgart, Germany

Received: 5 April 2002
Accepted: 3 June 2002

Abstract

We show that a general density functional approach for calculating the force between two big particles immersed in a solvent of smaller ones can describe systems that exhibit fluid-fluid phase separation: the theory captures effects of strong adsorption (wetting) and of critical fluctuations in the solvent. We illustrate the approach for the Gaussian core model, a simple model of a polymer mixture in solution and find extremely attractive, long-ranged solvent-mediated potentials between the big particles for state points lying close to the binodal, on the side where the solvent is poor in the species which is favoured by the big particles.