Optical microscopy, DSC and dielectric relaxation spectroscopy studies on a partially fluorinated ferroelectric liquid crystalline compound MHPO(13F)BC

Abstract

Phase transitions in a partially fluorinated compound, MHPO(13F)BC, have been studied by optical microscopy, calorimetry and miscibility methods. Spontaneous polarization (PS), helical pitch measurements, and frequency-domain dielectric study, have also been carried out. These studies indicate the presence of an intermediate alpha sub-phase between a ferroelectric and a paraelectric phase. Both the Goldstone-mode (GM) and the soft-mode (SM) relaxation processes have been observed, and by fitting the spectra to the Cole–Cole function, values of dielectric strengths, critical frequencies and dispersion parameters have been determined. Anomalies have been observed in the temperature dependence of PS and inverse dielectric strength, which are interpreted as a signature of a phase between the SmC∗ and SmA∗ phases. Microscopic patterns, helical pitch measurements, and miscibility studies give further evidence in support of this inference.