Influence of attractive forces on the solvent mediated potential of mean force between colloidal particles

The solvent induced potential of mean force between colloidal particles is computed by using the superposition approximation for the solvent-macrospheres triplet distribution function and the density functional theory for the solvent density profile at an isolated macrosphere. The influence of solute-solvent attractive forces is investigated for different diameter ratios and solvent bulk densities. For large colloidal particles, the mean force is shown to scale with the solvent-colloid hard core radius. At densities of liquid solvents, sufficient solvent-colloid attractions are found to strongly enhance the repulsive barriers in the potential of mean force and reduce the depth of the depletion well. At lower density, the mean force can become repulsive. Solvent-solvent attractions can suppress the oscillations in the potential and make it more attractive. These results are finally contrasted with those relative to purely repulsive interactions. (C) 1998 American Institute of Physics.