The Determination of the Elastic Constants of Nematic Liquid Crystals

Abstract The elastic constants K11 and K33 are calculated from the threshold field He associated with the Frederiks transition in a magnetic field of a uniform planar and a horneotropic layer, respectively. The elastic constant K22 is determined indirectly using a twisted planar layer.The errors associated with the determination of Hc are critically evaluated. In particular the anchoring conditions at the boundaries are found to have an important influence on Hc. Results for all three elastic constants of PAA and MBBA are given. In general our values for K11 and K33 are substantially higher than those reported in the literature.

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