Surface-directed spinodal decomposition

Abstract

We review analytical and numerical results for surface-directed spinodal decomposition (SDSD), namely, the interplay of wetting kinetics and phase separation in a binary (AB) mixture in contact with a surface S which prefers one of the components (say, A). Depending on the relative strengths of the A–B, A-S and B-S interactions, the surface is either partially wetted or completely wetted by A in equilibrium. We discuss the theoretical framework for modelling SDSD, and review results obtained from both microscopic and coarse-rained models. We clarify the differences between diffusion-driven SDSD in solids, and SDSD in fluids, where velocity fields play an important role. Furthermore, we discuss the dependence of wetting-layer kinetics on the composition of the mixture. Some results are also presented for phase separation in a confined geometry, e.g., thin films. Finally, we discuss the problem of surface-enrichment kinetics, namely, the kinetics of enrichment of an attracting surface when the bulk mixture is stable. These nonequilibrium processes have important applications in the preparation of nanomaterials and multi-layered structures.