Light scattering studies on the coil-globule phase transition of single polymers in solution

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1984.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE.Vita.Includes bibliographical references.by Gerald Adams Swislow.Ph.D

X-Ray Studies of the Surface and Bulk Structure of the Isotropic and Nematic Phase of a Lyotropic Liquid Crystal

We 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.Engineering and Applied Science