Capillary condensation and interface structure of a model colloid-polymer mixture in a porous medium

Paul P. F. Wessels, Matthias Schmidt, and Hartmut Löwen
Phys. Rev. E 68, 061404 – Published 17 December 2003
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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 small 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.

  • Received 29 July 2003

DOI:https://doi.org/10.1103/PhysRevE.68.061404

©2003 American Physical Society

Authors & Affiliations

Paul P. F. Wessels*

  • Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany

Matthias Schmidt

  • Debye Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands

Hartmut Löwen

  • Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany

  • *Electronic address: wessels@thphy.uni-duesseldorf.de
  • On leave from Institut für Theoretische Physik II, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.

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Issue

Vol. 68, Iss. 6 — December 2003

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