Wall-Induced Orientational Order of a Liquid Crystal in the Isotropic Phase—an Evanescent-Wave-Ellipsometry Study

Abstract

Using an evanescent-wave ellipsometric technique, we have studied the wall-induced orientational order in the isotropic phase of ${4}^{\ensuremath{'}}\ensuremath{-}n\ensuremath{-}\mathrm{pentyl}\ensuremath{-}4\ensuremath{-}\mathrm{cyanobiphenyl}$ (5CB) at a silane-treated glass surface. Near the isotropic-nematic transition temperature ${T}_{\mathrm{NI}}$, a weak nematic layer appears at the interface with its thickness exhibiting a critical divergence as $T\ensuremath{\rightarrow}{T}_{\mathrm{NI}}$ according to ${(T\ensuremath{-}{T}_{\mathrm{NI}})}^{\ensuremath{-}0.5}$. This observed pretransitional behavior is qualitatively at variance with the existing theories.