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 s urface. The disjoining pressure between the surfaces with a hydration- independent ''smearing'' does not differ from that of ''infinitely thi n'' 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 increas e the apparent decay length of the disjoining pressure by a factor of up to 2, in comparison with the bulk water correlations length, when t he in-plane correlations are long range. In the case of the short in-p lane correlations, the disjoining pressure decays with the inverse fou rth power of the intersurface separation, for all reasonable choices o f the surface smearing parameters.