Comparison of dynamic and static measurements of surface anchoring energy in nematic liquid crystals

We measured the surface anchoring energy of a nematic liquid crystal by a d ynamic light scattering experiment. A homogeneously aligned wedge-type cell with rubbed Nylon as the aligning layer and fined with the nematic 8CB was used. The spectrum of orientational fluctuations in confined liquid crysta l depends not. only on its bulk elasticity and viscosity but also on the su rface anchoring energy. If the surface extrapolation length is small compar ed to the sample thickness the relaxation time of the fundamental mode is s imply related to the inverse layer thickness. Fitting this relation to the measured relaxation times yields the azimuthal anchoring energy. The result s are compared with the ones obtained by static measurements in a twisted c ell. Here the surface anchoring energy is determined by the polarisation ro tation of a light beam passing through a nematic slab. We show that the Val ues of the surface anchoring energy obtained with both methods are in good agreement.