| Kurt Binder, D. Deb, A. Statt, P. Virnau and A. Winkler Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudinger Weg 7, D-55099 Mainz Abstract Colloid-Polymer mixtures are model systems, where the entropy-driven attraction between colloids can be tuned (with respect to its range and strength) via the size and the concentration of polymers in the suspension. Similarly, the attraction to planar walls can be modified by coating the latter with a suitable polymer brush layer. As a result, one expects that wettability of the walls (both at vapor-liquid and at liquid-solid type phase coexistence) can be controlled, at least in principle. We present Monte Carlo simulations to provide a theoretical guidance to this problem. It is shown that accurate estimates for the excess free energies due to walls in the various phases can be obtained via the \ensemble switch method", where a Hamiltonian mixed from a system with walls and without walls (and periodic boundary instead) is considered. The method is tested for the hard sphere fluid, where many estimates from alternative methods are available [1]. For vapor-liquid type coexistence in an Asakura-Oosawa model, where the liquid-vapor surface tension is known, Young's equation is used to demonstrate that conditions all the way from complete drying to complete wetting can be reached [2]. For liquid-solid coexistence, a comparison of the resulting prediction for the contact angle with observations from wall-attached crystalline “droplet" is made. References [1] D. Deb et al., J. Chem. Phys. 134, 214706 (2011) [2] A. Statt, A. Winkler, P. Virnau, and K. Binder, J. Phys.; Cond. Matter (in press) [3] D. Deb, A. Winkler, P. Virnau, and K. Binder, J. Chem. Phys. 136, 134710 (2012) |
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