Wetting behaviour of a model symmetric binary mixture with partially miscible components from a density functional approach

We investigate wetting transitions in a binary fluid at a solid surface by means of a density functional approach. For this purpose we use the symmetric binary mixture model, which exhibits a demixing in a bulk phase. We concentrate on the evaluation of the phase diagrams in the case of adsorption from a gas phase at a fixed composition. Our calculations have revealed different scenarios, leading to the change of wettability of the surface. In the case of adsorption from an equimolar bulk gas the wetting transition may be of the first or of the second order. In the case of non-equimolar bulk composition we observe either a transition from partial to complete wetting, or a first-order transition between two partial wetting states.