Capillary Condensation and Interface Structure of a Model Colloid-Polymer Mixture in a Porous Medium

Abstract

We consider the Asakura-Oosawa model of hard sphere colloids and ideal polymers in contact with a porous matrix modeled by immobilized configurations of hard spheres. For this ternary mixture a fundamental measure density functional theory is employed, where the matrix particles are quenched and the colloids and polymers are annealed, i.e. allowed to equilibrate. We study capillary condensation of the mixture in a tiny sample of matrix as well as demixing and the fluid-fluid interface inside a bulk matrix. Density profiles normal to the interface and surface tensions are calculated and compared to the case without matrix. Two kinds of matrices are considered: (i) colloid-sized matrix particles at low packing fractions and (ii) large matrix particles at high packing fractions. These two cases show fundamentally different behavior and should both be experimentally realizable. Furthermore, we argue that capillary condensation of a colloidal suspension could be experimentally accessible. We find that in case (ii), even at high packing fractions, the main effect of the matrix is to exclude volume and, to high accuracy, the results can be mapped onto those of the same system without matrix via a simple rescaling.

12 pages, 9 figures, submitted to PRE

References in corpus (4)

• Capillary condensation in disordered porous materials: hysteresis versus equilibrium behavior
• Influence of polymer excluded volume on the phase behavior of colloid-polymer mixtures
• Wetting at Curved Substrates: Non-Analytic Behavior of Interfacial Properties
• Percolation, depinning, and avalanches in capillary condensation of gases in disordered porous solids

Cited by in corpus (5)

• Phase behavior and structure of model colloid-polymer mixtures confined between two parallel planar walls
• Replica Density Functional Study of One-Dimensional Hard Core Fluids in Porous Media
• First-principles derivation of density functional formalism for quenched-annealed systems
• Diffusion of Colloidal Fluids in Random Porous Media
• Fluid phase separation inside a static periodic field: an effectively two-dimensional critical phenomenon