Wetting of liquid-crystal surfaces and induced smectic layering at a nematic-liquid interface: an x-ray reflectivity study.

摘要: We report the results of a synchrotron x-ray reflectivity study bulk liquid-crystal surfaces that are coated by thin wetting films an immiscible liquid. The subphase consisted nematic or isotropic phase 4-octyl- 4;{'} -cyanobiphenyl (8CB), and film was formed fluorocarbon perfluoromethylcyclohexane (PFMC), volatile thickness controlled temperature difference DeltaT(micro) between sample reservoir PFMC, contained within sealed cell. Phase information on interfacial electron density profiles has been extracted from interference scattering PFMC-vapor interface surface-induced smectic order 8CB subphase. side nematic-liquid (8CB-PFMC) is characterized oscillation whose period corresponds to layer spacing amplitude decays exponentially toward underlying decay length xi independent PFMC but increases as nematic-smectic- A transition T(NA) approached, in agreement with longitudinal correlation xi(parallel) proportional, variant(T-T(NA))(-0.7} for fluctuations nematic. indicate homeotropic orientation molecules preferred at 8CB-PFMC observed dependence growth consistent critical adsorption mechanism. thickness, L variant(DeltaT(micro))(-1/3) , implies completely wets surface dominated nonretarded dispersion interactions hydro- fluorocarbons. complete behavior nearly degree