Critical Casimir Forces and Colloidal Phase Transitions in a Near-Critical Solvent : A Simple Model Reveals a Rich Phase Diagram

Abstract

From experimental studies it is well-known that colloidal particles suspended in a near-critical binary solvent exhibit interesting aggregation phenomena, often associated with colloidal phase transitions, and assumed to be driven by long-ranged solvent mediated (SM) interactions (critical Casimir forces), set by the (diverging) correlation length of the solvent. We present the first simulation and theoretical study of an explicit model of a ternary mixture that mimics this situation. Both the effective SM pair interactions and the full ternary phase diagram are determined for Brownian discs suspended in an explicit two-dimensional supercritical binary liquid mixture. Gas-liquid and fluid-solid transitions are observed in a region that extends well-away from criticality of the solvent reservoir. We discuss to what extent an effective pair-potential description can account for the phase behavior we observe. Our study provides a fresh perspective on how critical fluctuations of the solvent might influence colloidal self-assembly.

arXiv comment4 pages, 4 figures

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• Anisotropic scaling of the two-dimensional Ising model I: the torus
• Dynamics and steady states of a tracer particle in a confined critical fluid
• Experimental and Theoretical Bulk Phase Diagram and Interfacial Tension of Ouzo
• Effective Pair Interaction of Patchy Particles in Critical Fluids
• Sign change in the net force in sphere-plate and sphere-sphere systems immersed in nonpolar critical fluid due to the interplay between the critical Casimir and dispersion van der Waals forces
• On The Critical Casimir Interaction Between Anisotropic Inclusions On A Membrane
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• The square lattice Ising model on the rectangle III: Hankel and Toeplitz determinants
• Discontinuous change from thermally- to geometrically- dominated effective interactions in colloidal solutions
• Critical Casimir Interactions and Percolation: the quantitative description of critical fluctuations
• Entropic magnetic interlayer coupling