Swislow, G.Schwartz, D.Ocko, B. M.Pershan, PeterLitster, J. D.2013-03-011991Swislow, G., D. Schwartz, B. M. Ocko, Peter S. Pershan, and J. D. Litster. 1991. X-ray studies of the surface and bulk structure of the isotropic and nematic phase of a lyotropic liquid crystal. Physical Review A 43(12): 6815-6825.1050-2947http://nrs.harvard.edu/urn-3:HUL.InstRepos:10357548We have used x-ray specular reflection to study the structure of the air–liquid-crystal interface of the lyotropic liquid crystal formed from binary mixtures of cesium perfluoro-octanoate (CsPFO) and water. In the isotropic phase the surface is coated with a monolayer of CsPFO separated by layers of water from one or more smectic bilayers of CsPFO. As for the case of thermotropic liquid crystals, the isotropic-to-nematic phase transition has no effect on the surface structure, and as the temperature is lowered towards the nematic–to–smectic-A transition temperature, the number of surface-induced smectic layers increases dramatically (e.g., approximately 100 layers were observed). Theoretical modeling of the reflectivity excludes the possibility that the surface bilayers are arrays of micelles. X-ray scattering from critical smectic short-range order in the bulk, studied by tuning the spectrometer away from the specular condition, indicates that the scattering is fundamentally different from short-range smectic order in thermotropic systems.en-USJournal Article10.1103/PhysRevA.43.6815