Anchoring strength of a lyotropic nematic liquid crystal

We determine the anchoring strength (W) for a lyotropic liquid crystal in the nematic calamitic phase. The sample holder is a microslide 200 μm thick (Vitro Dynamics) whose inner surfaces present some grooves introducing an easy axis. The technique used is based on the determination of the critical magnetic field for a Frederiks transition. The values obtained are W∼${10}^{\mathrm{-}3}$ erg/${\mathrm{cm}}^2$ and the extrapolation length L∼6 μm.