Liquid–liquid equilibrium in a slit pore: Monte Carlo simulation and mean field density functional theory

Monte Carlo simulations and mean field density functional theory have been used to study the behavior of a model liquid mixture in a slit pore. The mixture is symmetric with a weakened attractive interaction between the unlike species and exhibits liquid–liquid equilibrium with an upper critical solution temperature. We have studied the influence of confinement on this phase equilibrium. The components have the same interaction with the pore walls, but a lowering of dimensionality in the pore causes selective adsorption of the dilute component. The critical temperature is lowered by the confinement in a manner which is qualitatively consistent with earlier work on the Ising model between walls. The effects are also similar to those seen in recent experimental and theoretical work on thin polymer blend films.