Flexoelectric Domains in a Binary Mixture of Nematics

The formation of flexoelectric domains in a mixture of nematic liquid crystals N-(4-Methoxybenzylidene)-4-butylaniline and 4-Cyano-4'-pentylbiphenyl with the permittivity anisotropy ε a ≈ 0 under dc voltage has been investigated. The threshold characteristics of the domain structure (threshold voltage and spatial period) in this mixture have been measured. The difference in the flexoelectric coefficients | e 1 – e 3 | is estimated. It is shown that the threshold voltage in the mixture of nematic liquid crystals with ε a ≈ 0 is determined only by the ratio k /( e 1 – e 3 ), where k is the average elasticity constant. This fact makes it possible to calculate directly the difference in the flexoelectric coefficients | e 1 – e 3 |, excluding surface properties. The proposed and approved method for determining the flexoelectric coefficients can be useful for new synthesized nematic liquid crystals with ε a < –0.5.