Elastic and dielectric constants in mixtures of nematic liquid crystals

The dielectric constants and two elastic constants were measured for a series of mixtures of two nematic liquid crystals, MBBA and PEBAB. The materials covered the range from 0 to 10% PEBAB. The parameters were calculated from the measured voltage dependence of capacitance. The dielectric constants vary linearly with PEBAB concentration and the anisotropy changes from negative to positive at 1.7%. The elastic constants remain fixed over most of the range, but are reduced in mixtures of small anisotropy. The results differ significantly from recent measurements of Michel and Smith, the probable reason being that we take any nonideal alignment at the surface explicitly into account in the calculations.