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51.

Competition between sedimentation and phase coexistence of colloidal dispersions under gravity M. Schmidt, M. Dijkstra, and J.-P. Hansen, J. Phys.: Condens. Matt. 16, S4185 (2004). Locate in [bare] [illustrated] list. Get [full paper] as pdf. Abstract. After a brief review of the theory of sedimentation equilibria of colloidal systems, we consider the specific case of binary systems of hard sphere colloids and non-interacting polymer coils, the latter of vanishing buoyancy mass. The density profiles of the two components are calculated within density functional theory and using Monte Carlo simulations. Under appropriate conditions the profiles exhibit discontinuities or steeply varying regions associated with the interface separating colloid-rich and colloid-poor phases. The position of the interface is shown to be very sensitive to the strength of the gravitational field and, more surprisingly, to the total height L of the suspension. Phase coexistence in the absence of gravity is shown to be entirely suppressed beyond a critical ratio of the height L over the gravitational length of the colloids. [figures] Read the [full paper] as pdf.

Fluid interfaces

Colloid-polymer mixtures display fluid-fluid interfaces [21] [44], relevant for laser-induced condensation [35], capillary condensation [43] and evaporation [48], immersion in porous media [41], the appearance of the floating liquid phase [52], the competition between sedimentation and phase coexistence [51], tension at a substrate [45], the experimental observation of thermal capillary waves [47], and the contact angle of the liquid-gas interface and a wall [50]. In colloidal rod-sphere mixtures fluid-fluid interfaces were investigated with theory [30] and simulation [42]. Hard sphere fluids were considered at surfaces of porous media [37], in random fiber networks [39], and in one dimensional cases [46].



Hard spheres

The hard sphere system freezes between [2] and [3], and in ~[23] dimensions (tags as contents!), as well as on stripe-patterned substrates [26]. Deep relations to dimensional crossover exist [5] [6]. Hard spheres were immersed in emulsions [9], confined to a flexible container [18], exposed to surfaces of other quenched spheres [37] and of random fiber networks [39], and subject to gravity [51]. Recently, the Rosenfeld functional [5] [6] was generalized to non-additive mixtures [53].

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