Comparison of Dynamic and Static Measurements of Surface Anchoring Energy in Nematic Liquid Crystals

摘要

We measured the surface anchoring energy of a nematic liquid crystal by a dynamic light scattering experiment. A homogeneously aligned wedge-type cell with rubbed Nylon as the aligning layer and filled with the nematic 8CB was used. The spectrum of orientational fluctuations in confined liquid crystal depends not only on its bulk elasticity and viscosity but also on the surface anchoring energy. If the surface extrapolation length is small compared to the sample thickness the relaxation time of the fundamental mode is simply related to the inverse layer thickness. Fitting this relation to the measured relaxation times yields the azimuthal anchoring energy. The results are compared with the ones obtained by static measurements in a twisted cell. Here the surface anchoring energy is determined by the polarisation rotation of a light beam passing through a nematic slab. We show that the values of the surface anchoring energy obtained with both methods are in good agreement.