The limits of flexoelectricity in liquid crystals

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Conformational flexoelectricity in nematic liquid crystals

2014 Using the direct flexoelectric effect in an hybrid (homeotropic-planar) nematic cell, we have measured the bulk flexoelectric coefficient e* for two cyanobiphenyl compounds, 8CB and 8OCB. For 8CB, the flexo coefficient is comparable in sign and magnitude with that of MBBA, i.e. e* ~ + 10-4 cgs. 8OCB presents an anomalously large and negative e* ~ 5 x 10-4 cgs. The small influence of the cy...

Statistical mechanics of splay flexoelectricity in nematic liquid crystals.

We develop a lattice model for the splay flexoelectric effect in nematic liquid crystals. In this model, each lattice site has a spin representing the local molecular orientation, and the interaction between neighboring spins represents pear-shaped molecules with shape polarity. We perform Monte Carlo simulations and mean-field calculations to find the behavior as a function of interaction para...

Giant flexoelectricity of bent-core nematic liquid crystals.

Flexoelectricity is a coupling between orientational deformation and electric polarization. We present a direct method for measuring the flexoelectric coefficients of nematic liquid crystals (NLCs) via the electric current produced by periodic mechanical flexing of the NLC's bounding surfaces. This method is suitable for measuring the response of bent-core liquid crystals, which are expected to...

Flexoelectricity and pattern formation in nematic liquid crystals.

We present in this paper a detailed analysis of the flexoelectric instability of a planar nematic layer in the presence of an alternating electric field (frequency ω), which leads to stripe patterns (flexodomains) in the plane of the layer. This equilibrium transition is governed by the free energy of the nematic, which describes the elasticity with respect to the orientational degrees of freed...