Statistical mechanics of adsorption and wetting

The adsorption and wetting behavior of fluids on solid surfaces and at fluid-fluid interfaces are consequential in numerous natural processes and technological applications. Though the scientific study of the subject is old, going back to the early nineteenth century when Young and Laplace identified the laws of capillarity, the molecular theory of interfacial phenomena is still a developing subject. It has been given a rigorous statistical mechanical foundation through the now classic works of Kirkwood, Buff and coworkers, the recent progress in the density functional theory of inhomogeneous systems, and the renormalization group theory of critical phenomena. It is interesting that perhaps the most fruitful development in the theory of interfacial phenomena has been the revival of the mean field theory of van der Waals. While not rigorous, this theory is tractable, has provided the insight and motivation for many useful new theories, and captures most of the known qualitative patterns of interfacial behavior, except for details near a critical point where renormalization group theory is required. Because of its simplicity and qualitative successes, van der Waals theory was chosen as the main vehicle for presentation of an overview of our current understanding of adsorption and wetting.