Pretransitional nematic surface order in the isotropic phase of phenylcyclohexanes

Pretransitional order at the free surface of the isotropic phases of two phenylcyclohexances (PCH5 and PCH7) was studied by reflection ellipsometry under variation of the angle of incidence. Data analysis shows a logarithmic divergence of the boundary layer thickness when the temperature approaches the isotropic-nematic transition point, indicating complete wetting behavior. The data are well represented by fits to a model based on a Landau–de Gennes approach, yielding order parameter profiles of the layer.