Measurement of Flexoelectric Coefficients of Some Nematic Liquid Crystals

As we have discussed in Chapter I of this thesis, the nematic director is apolar. IIence the usual dielectric coupling with an external electric field depends quadratically on the latter. However, as has been discussed earlier a deformed director field with a splay and/or bend distortion can lead to a flexoelectric polarisation of the medium. The response of liquid crystals to an electric field under many circumstances is influenced by the flexoelectric effect. In this case the coupling is linear with the applied electric field as well as the curvature of the director field. In fact this special feature produces many interesting effects on electrohydrodynamic (EHD) instabilities (Madhusudana et al., 1987,1989; ~ a ~ h u n a t h a h et al., 1991), whicll has been discussed in the previous chapters.