Dielectric method for determining the rotational viscosity in thick samples of ferroelectric chiral smectic-C*liquid crystals

An alternative method, based on dielectric measurements on thick samples, for determining the Goldstone-mode rotational viscosity and the twist elastic constant of ferroelectric, chiral smectic-${\mathit{C}}^{\mathrm{*}}$ liquid crystals is presented. By the use of this method the temperature dependence of these quantities for p-decyloxibenzilidine-p’-amino-1-methylpropyl-cinamate (DOBA-1-MPC) and p-n-decyloxybenzylidine-p-amino-2-methyl-butyl-cinamate (DOBAMBC) has been determined. An Arrhenius-type behavior of the Goldstone-mode rotational viscosity was obtained with activation energies μ=0.33 eV for DOBA-1-MPC and μ=0.51 eV for DOBAMBC.