Surface-induced pretransitional order in the isotropic phase near the isotropic-nematic phase transition

We have studied the formation of a nematic layer in the isotropic phase of members of the homologous series of alkylcyanobiphenyl liquid crystals (nCB, n = 5-12) near a polyamide-coated glass surface. From the temperature dependence near the isotropic-nematic transition of the standard ellipsometric quantity Delta, which is directly related to the residual birefringence, the wetting behaviour of the nematic layer was investigated using a high precision rotating analyser ellipsometer. In contrast to the results of Chen et al., who observed a wetting transition for nCB-DMOAP-glass systems, our results indicate that for the nCB-polyamide-glass configurations the wetting is always partial.