Dielectric properties of liquid crystal formed by laterally fluorine-substituted banana-shaped molecules

Abstract

ABSTRACT Dielectric spectroscopy in the frequency range from 10−2 to 107 Hz was applied to investigate the dynamics of the relaxation processes in a banana-shaped liquid crystal compound with fluorinated chain segments. The dielectric spectra indicate the presence of two relaxation processes and a conductivity contribution. The high-frequency process shows Arrhenius-like temperature dependence in the B4 and SmCP phases and can be assigned to the hindered rotation of the bent-shaped molecules around their long molecular axis. The low-frequency process can be related to the dynamics of the periodic superstructures in B4 phase and fluctuations of the modulated ferroelectric domains in the SmCP phase. In the B7 (or SmCG) phase, both processes show the nonlinear dependence of the relaxation frequencies especially close to the isotopic phase transition. The dielectric measurements confirm the existence of the SmCP – B7 (or SmCG) second order or weakly first-order phase transition.