EFFECTS OF THE INTERFACIAL STRUCTURE ON THE HYDRATION FORCE BETWEEN LATERALLY NONUNIFORM SURFACES

Hydration-dependent repulsion of polar surfaces is studied within the framework of a nonlocal electrostatic model. Allowance is made for the transversal distribution of the water binding sites in such surfaces, as well as for the lateral correlations between these sites on each surface. The disjoining pressure between the surfaces with a hydration-independent ''smearing'' does not differ from that of ''infinitely thin'' interfaces, except for the appearance of a pre-exponential factor. The hydration-dependent interfacial smearing, that is, the solvation-dependent corrugation and softness of the surface, is found to increase the apparent decay length of the disjoining pressure by a factor of up to 2, in comparison with the bulk water correlations length, when the in-plane correlations are long range. In the case of the short in-plane correlations, the disjoining pressure decays with the inverse fourth power of the intersurface separation, for all reasonable choices of the surface smearing parameters.