Publication: Surface and smectic layering transitions in binary mixtures of parallel hard rods
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2010-02
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The American Physical Society
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Abstract
The surface phase behavior of binary mixtures of colloidal hard rods in contact with a solid substrate (hard wall) is studied, with special emphasis on the region of the phase diagram that includes the smectic A phase. The colloidal rods are modeled as hard cylinders of the same diameter and different lengths, in the approximation of perfect alignment. A fundamental-measure density functional is used to obtain equilibrium density profiles and thermodynamic properties such as surface tensions and adsorption coefficients. The bulk phase diagram exhibits nematic-smectic and smectic-smectic demixing, with smectic phases having different compositions; in some cases they are microfractionated. The calculated surface phase diagram of the wall-nematic interface shows a very rich phase behavior, including layering transitions and complete wetting at high pressures, whereby an infinitely thick smectic film grows at the wall via an infinite sequence of stepwise first-order layering transitions. For lower pressures complete wetting also obtains, but here the smectic film grows in a continuous fashion. Finally, at very low pressures, the wall-nematic interface exhibits critical adsorption by the smectic phase, due to the second-order character of the bulk nematic-smectic transition.
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12 pages, 13 figures.-- PACS nrs.: 64.70.M-, 61.30.Hn, 61.20.Gy, 64.75.Xc.-- ArXiv pre-print available at: http://arxiv.org/abs/1002.0512
Keywords
[PACS] Transitions in liquid crystals, [PACS] Surface phenomena: alignment, anchoring, anchoring transitions, surface-induced layering, surface-induced ordering, wetting, prewetting transitions, and wetting transitions, [PACS] Theory and models of liquid structure, [PACS] Phase separation and segregation in colloidal systems
Bibliographic citation
Physical Review E 81, 021706 (2010)