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Effect of many-body interactions on the bulk and interfacial phase behavior of a model colloid-polymer mixture

Dijkstra, M, Van Roij, R, Roth, R and Fortini, A (2006) Effect of many-body interactions on the bulk and interfacial phase behavior of a model colloid-polymer mixture Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 73 (4).

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We study a model suspension of sterically stabilized colloidal particles and nonadsorbing ideal polymer coils, both in bulk and adsorbed against a planar hard wall. By integrating out the degrees of freedom of the polymer coils, we derive a formal expression for the effective one-component Hamiltonian of the colloids. We employ an efficient Monte Carlo simulation scheme for this mixture based on the exact effective colloid Hamiltonian; i.e., it incorporates all many-body interactions. The many-body character of the polymer-mediated effective interactions between the colloids yields bulk phase behavior and adsorption phenomena that differ substantially from those found for pairwise simple fluids. We determine the phase behavior for size ratios q= σp σc =1, 0.6, and 0.1, where σc and σp denote the diameters of the colloids and polymer coils, respectively. For q=1 and 0.6, we find both a fluid-solid and a stable colloidal gas-liquid transition with an anomalously large bulk liquid regime caused by the many-body interactions. We compare the phase diagrams obtained from simulations with the results of the free-volume approach and with direct simulations of the true binary mixture. Although we did not simulate the polymer coils explicitly, we are able to obtain the three partial structure factors and radial distribution functions. We compare our results with those obtained from density functional theory and the Percus-Yevick approximation. We find good agreement between all results for the structure. We also study the mixture in contact with a single hard wall for q=1. Upon approach of the gas-liquid binodal, we find far from the triple point, three layering transitions in the partial wetting regime. © 2006 The American Physical Society.

Item Type: Article
Divisions : Surrey research (other units)
Authors :
Dijkstra, M
Van Roij, R
Roth, R
Date : 21 April 2006
DOI : 10.1103/PhysRevE.73.041404
Depositing User : Symplectic Elements
Date Deposited : 17 May 2017 13:17
Last Modified : 24 Jan 2020 23:44

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