Permittivity, Conductivity, Elasticity, and Viscosity Measurements in the Nematic Phase of a Bent-Core Liquid Crystal

We report on measurements of dielectric permittivity epsilon, electrical conductivity sigma, elastic moduli k(ii), and rotational viscosity gamma for a bent-core nematic liquid crystal. The static permittivity anisotropy epsilon(a)=epsilon(parallel to) - epsilon(perpendicular to) is negative; at a given temperature in the interval 107- 123 degrees C, epsilon(parallel to) shows two relaxations falling in the frequency bands 20-200 kHz and 0.9-2 MHz; epsilon(perpendicular to) also shows a relaxation between 0.9 and 5 MHz. The conductivity anisotropy sigma(n) = sigma(parallel to) - sigma(perpendicular to) is negative at low frequencies; it changes sign twice at frequencies f(1) and f(2) that increase with temperature, in the ranges 6.5-10 and 95-600 kHz, respectively. Surprisingly, the splay modulus k(11) is considerably greater than the bend modulus k(33) in the entire nematic range. Viscous relaxation is more complex than in calamitic systems involving at least a two-step process. The gamma values are an order of magnitude greater compared to calamities.