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

Using an evanescent-wave ellipsometric technique, we have studied the wall-induced orientational order in the isotropic phase of $4^{\prime }-n-\mathrm{pentyl}-4-\mathrm{cyanobiphenyl}$ (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 $T\to T_{\mathrm{NI}}$ according to ${(T-T_{\mathrm{NI}})}^{-0.5\mathrm{}}$. This observed pretransitional behavior is qualitatively at variance with the existing theories.