Onset and evolution of the tilted smectic antiphase in a polar liquid-crystal binary mixture.

Abstract

High-resolution x-ray diffraction studies of a binary mixture of the n=8 and n=10 homologs of alkoxyphenyl nitrobenzoyloxy benzoate ${\mathrm{DB}}_{\mathit{n}}$${\mathrm{ONO}}_{2}$ (52.6 mole % ${\mathrm{DB}}_{10}$${\mathrm{ONO}}_{2}$) have been performed at the onset of the tilted smectic antiphase (Sm-C\ifmmode \tilde{}\else \~{}\fi{}) upon cooling from the smectic-${\mathit{A}}_{1}$ phase. Fluctuations of the two competing smectic orders are found to be related to monolayer and partial bilayer ordering. With decreasing temperature, the period of the antiphase in-plane modulation increases while the smectic layer normal tilts at an angle of \ifmmode\pm\else\textpm\fi{}7\ifmmode^\circ\else\textdegree\fi{} with respect to the director. This tilt partially recovers upon the transition to the smectic-${\mathit{A}}_{2}$ phase. \textcopyright{} 1996 The American Physical Society.