Abstract
A scenario of continuous and discontinuous wetting transitions is predicted by the continuum theory of dispersion forces, which is different from that obtained by an addition of the nonretarded van der Waals interaction with a next-to-leading term. It is found that the transition temperatures of continuous wetting transitions are higher than the temperature where the nonretarded van der Waals interaction changes its sign. For van der Waals systems the macroscopic dielectric properties of the materials participate in determining not only the existence but also the order of a wetting transition.