MONTE-CARLO SIMULATION STUDY OF ADSORPTION FROM A LIQUID-MIXTURE AT STATES NEAR LIQUID-LIQUID COEXISTENCE

We present a Monte Carlo simulation study of adsorption on a plane solid surface from a model binary liquid mixture with a miscibility gap terminating at an upper critical solution temperature. The model liquid mixture studied is a binary Lennard-Jones 12-6 mixture with identical pure components but with a weak unlike interaction. The components interact with the solid surface by means of 9-3 potentials. Adsorption isotherms in the approach to liquid-liquid coexistence from the phase dilute in the strongly adsorbed component have been found which are consistent with the presence of partial wetting and complete wetting by the more strongly adsorbed phase at coexistence. In addition prewetting transitions have been found. Resolution of the prewetting transition was made possible by using an isobaric semigrand ensemble, which for the system under consideration allows a precise tuning of the bulk state relative to saturation.