X-ray determination of the molecular tilt and layer fluctuation profiles of freely suspended liquid-crystal films

Abstract

X-ray diffraction has been used to study the interlayer structure of fluid freely suspended liquid-crystal films versus film thickness. The observed scattering is described extremely well by a simple interlayer density model based on predicted layer fluctuation ${\mathrm{\ensuremath{\sigma}}}_{\mathit{i}}$ and tilt angle ${\mathrm{\ensuremath{\varphi}}}_{\mathit{i}}$ profiles. The diffraction data determine the individual ${\mathrm{\ensuremath{\sigma}}}_{\mathit{i}}$'s to about \ifmmode\pm\else\textpm\fi{}0.1 \AA{}, and the layer-fluctuation profiles calculated for the hydrodynamic fluctuations agree to this precision. The tilt profiles calculated using a simple elastic theory are also in excellent agreement with the data.