Integral Equation Study of the Solvation Force between Macroscopic Surfaces Separated by Thin Films of Diatomic, Chain, and Network Solvents

The simple models of associating fluids, i.e., hard spheres with one, two, and four surface-located associatively interacting sites are employed in the singlet approach of integral equation theory to probe the effects of the nonsphericality of solvent molecules: linear and branched (or network) chain formations in the solvent on the interaction between two immersed macroscopic surfaces. We found that the obtained results qualitatively reproduce the most important experimentally observed features of the solvation force. We see what may be called negative solvation forces between macroscopic surfaces in a linear chain solvent, whereas in the case of the network solvent, the solvation force is nearly monotonic, positive, and repulsive at short separations.