Phase behavior of colloid-polymer mixtures in planar, spherical, and cylindrical confinement: A density functional...

The Asakura-Oosawa (AO) model of colloid-polymer mixtures has been extensively studied over the past several decades both via computer simulations and Density Functional Theory (DFT). At this point, its structural and thermodynamic properties both in the bulk and in contact with flat structureless walls are well understood. At the same time, the phase behavior of AO mixtures in spherical cavities and cylindrical pores, while thoroughly investigated by simulations, has not received a comparably detailed DFT treatment. In this paper, we use the DFT results for the AO model in the bulk and under planar confinement as a point of reference for studying its thermodynamic and structural properties in cavities and pores. The accuracy of the DFT approach is assessed by comparing its predictions with the available extensive simulation data; good overall agreement is generally found with some notable exceptions in the vicinity of wetting and drying transitions. The deviations of the phase behavior in confinement from the bulk phase diagram are analyzed using the Kelvin equation, which is seen to work reasonably well under moderate confinement, i.e., for sufficiently large radii of confining cavities and pores.