Dielectric dispersion in a dual-frequency smectic A liquid crystal PPEP(3F6)-CN/P(CN)P6-6 mixture

Abstract

This study examined the effects of temperature on the dielectric dispersion of cells holding a PPEP(3F6)-CN/P(CN)P6-6 mixture in the smectic A phase with homeotropic or homogeneous alignments, employing frequencies from 100 Hz to 1 MHz. The Cole–Cole function in conjunction with the DC conductivity was employed to assess these dispersion. In the mixture, it was observed that the dielectric anisotropy changed its sign depending on the frequency. This is the first observation of such a dual-frequency characteristic in the smectic phase to the best of our knowledge, although some dual-frequency nematic liquid crystals have been reported thus far. The value of the crossover frequency, where the sign of the anisotropy was observed to change, was determined to be correlated with the relaxation frequency, for the specimen.

Dielectric anisotropy in liquid crystal mixtures with nematic and smectic phases

“…The crossover frequency ( f c ) is a critical parameter in DFLCs that determines the sign of ∆ε, being positive when the electric field frequency is below f c and negative when above. [25] Previous studies on DFLCs have primarily focused on the nematic phase [14,26] and interesting works have been conducted in cholesteric liquid by Lee et al [27] However, recent observations by Kosuke Kaneko et al [28] revealed dualfrequency characteristics in the smectic A phase over a wide temperature range in a mixed LC system. Despite this advancement, a systematic investigation of dual-frequency mixed LCs with varying ratios has not been conducted.…”