The refractive indices of E7 liquid-crystal mixture were measured at six visible and two infrared (lambda=1.55 and 10.6 mu m) wavelengths at different temperatures, using Abbe and wedged cell refractometer methods, respectively. The experimental data of the visible wavelengths fit the extended Cauchy equations well. Using the extended Cauchy equations, we can extrapolate the refractive indices of E7 to IR. The extrapolated results almost strike through the measured data. Thus, the extended Cauchy equations can be used to link the visible refractive indices to infrared, where the refractive index measurements are more difficult. (C) 2005 American Institute of Physics

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The anchoring energy at the interface between the nematic liquid crystal 4-n -pentyl-4'cyanobiphenyl (5CB) and a glass plate treated by oblique evaporation of SiO is studied by measurement of the torque exerted on the surface by the nematic subject to an orienting magnetic field. The anchoring energy is sharply reduced as the clearing temperature is approached. The experiment provides the first direct evidence of a strong reduction of the surface order parameter for this system in the anisotropic phase.

In this paper we report an experimental investigation on the dynamics of the azimuthal director reorientation at a nematic-solid interface. Three qualitatively different kinds of substrates have been investigated: I) intrinsically anisotropic SiO-substrates (60 degrees-evaporation), II) isotropic SiO-substrates (0 degrees-evaporation) and III) rubbed PVA-substrates. In the case II), an in-plane anisotropy was induced cooling; slowly the thermotropic nematic liquid crystal (NLC) from the isotropic phase in the presence of a 0.75 T magnetic field. The reorientation dynamic of the surface azimuthal director angle at the switching-on and off of a magnetic (or electric) field has been investigated. All the substrates show comparable azimuthal anchoring energies and two dynamic regimes: a fast dynamic response, driven by the bulk director reorientation and an extremely slow reorientation. The slow dynamics is explained in terms of anisotropic adsorption of NLC molecules on the solid substrate and is well represented by a stretched exponential