Spontaneous Polarization and Dielectric Relaxation Dynamics of Two Novel Diastereomeric Ferroelectric Liquid Crystals

摘要

This study reports on the spontaneous polarization and molecular dynamics of two diastereomeric ferroelectric liquid crystals with a phenyl core ring but with different types of diastereomeric structures. The magnitudes of spontaneous polarization, measured via an Automated LC Property Tester, were similar for the two ferroelectric liquid crystals. The complex dielectric spectra, measured via an impedance analyzer, indicated the existence of the Goldstone mode in the ferroelectric (SmC*) phase for the two ferroelectric liquid crystals. Moreover, a novel ferrielectric-like (SmC gamma*-like) phase was observed at certain temperatures. The complex dielectric spectra of the two ferroelectric liquid crystals were optimally analyzed by a theoretical model composed of the Debye model and the Cole-Cole model. The physical parameters such as relaxation frequency and dielectric strength were determined by a dielectric relaxation study, and the obtained parameters varied in accordance with phase transition sequence. The experimental results of dielectric spectra and spontaneous polarization are explained in the discussion of the mesomorphic properties related to the ferroelectric liquid crystal molecular structure.