Wetting of Liquid-Crystal Surfaces and Induced Smectic Layering at a Nematic-Liquid Interface: An X-ray Reflectivity Study
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Wetting of Liquid-Crystal Surfaces and Induced Smectic Layering at a Nematic-Liquid Interface: An X-ray Reflectivity Study
| Title: | Wetting of Liquid-Crystal Surfaces and Induced Smectic Layering at a Nematic-Liquid Interface: An X-ray Reflectivity Study |
| Author: |
Fukuto, Masafumi; Gang, Oleg; Alvine, Kyle J.; Ocko, Benjamin M.; Pershan, Peter S.
Note: Order does not necessarily reflect citation order of authors. |
| Citation: | Fukuto, Masafumi, Oleg Gang, Kyle J. Alvine, Benjamin M. Ocko, and Peter S. Pershan. 2008. Wetting of liquid-crystal surfaces and induced smectic layering at a nematic-liquid interface: An x-ray reflectivity study. Physical Review E 77(031607). |
| Access Status: | At the direction of the depositing author this work is not currently accessible through DASH. |
| Full Text & Related Files: |
Fukuto_Wetting.pdf (700.6Kb; PDF) 
|
| Abstract: | We report the results of a synchrotron x-ray reflectivity study of bulk liquid-crystal surfaces that are coated by thin wetting films of an immiscible liquid. The liquid-crystal subphase consisted of the nematic or isotropic phase of 4-octyl-4′-cyanobiphenyl (8CB), and the wetting film was formed by the fluorocarbon perfluoromethylcyclohexane (PFMC), a volatile liquid. The thickness of the wetting film was controlled by the temperature difference ΔTμ between the sample and a reservoir of bulk PFMC, contained within the sealed sample cell. Phase information on the interfacial electron density profiles has been extracted from the interference between the scattering from the PFMC-vapor interface and the surface-induced smectic order of the 8CB subphase. The liquid-crystal side of the nematic-liquid (8CB-PFMC) interface is characterized by a density oscillation whose period corresponds to the smectic layer spacing and whose amplitude decays exponentially toward the underlying nematic subphase. The decay length ξ of the smectic amplitude is independent of the PFMC film thickness but increases as the nematic–smectic-A transition temperature TNA is approached, in agreement with the longitudinal correlation length ξ∥∝(T−TNA)−0.7 for the smectic fluctuations in the bulk nematic. The results indicate that the homeotropic orientation of the 8CB molecules is preferred at the 8CB-PFMC interface and that the observed temperature dependence of the smectic layer growth is consistent with the critical adsorption mechanism. The observed ΔTμ dependence of the PFMC film thickness, L∝(ΔTμ)−1/3, implies that PFMC completely wets the 8CB surface and is dominated by the nonretarded dispersion interactions between hydro- and fluorocarbons. The complete wetting behavior of PFMC is nearly independent of the degree of interfacial smectic order in the subphase. |
| Published Version: | doi:10.1103/PhysRevE.77.031607 |
| Other Sources: | http://liquids.seas.harvard.edu/peter/2008.pdf/Masa_lx.pdf |
| Citable link to this page: | http://nrs.harvard.edu/urn-3:HUL.InstRepos:4726290 |
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Peer reviewed scholarly articles from the Faculty of Arts and Sciences of Harvard University
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