Entropic wetting of a colloidal rod-sphere mixture

R. Roth; J. M. Brader; M. Schmidt

doi:doi:10.1209/epl/i2003-00563-6

DOI: 10.1209/epl/i2003-00563-6
Europhys. Lett., 63 (4) , pp. 549-555 (2003)

Entropic wetting of a colloidal rod-sphere mixture

R. Roth^{1, 2}, J. M. Brader³ and M. Schmidt⁴

¹ Max-Planck-Institut für Metallforschung - Heisenbergstr. 3, 70569 Stuttgart, Germany
² ITAP, Universität Stuttgart - Pfaffenwaldring 57, 70569 Stuttgart, Germany
³ Institute of Physiology, University of Bern - Bühlplatz 5, 3012 Bern, Switzerland
⁴ Soft Condensed Matter, Debye Institute, Utrecht University Princetonpln 5, 3584 CC Utrecht, The Netherlands

(Received 28 March 2003; accepted in final form 16 June 2003)

Abstract
We investigate the behavior of a model colloidal mixture of hard spheres and rod-like particles near a planar hard wall using density functional theory. For small size ratios of rod length and sphere diameter we find that the colloidal liquid phase wets the wall completely upon approaching the fluid demixing binodal from the colloidal gas side, provided the density of the rods lies below the wetting point. Using an effective one-component description based on the pairwise depletion potential for higher density of rods, a finite sequence of layering phase transitions is found. For large rod-to-sphere size ratios, using a binary treatment, thick films are obtained even close to the triple point.