Characteristics of the dielectric relaxation modes of a newly synthesized fluorinated antiferroelectric liquid crystal 6F6B

The dielectric response of a newly synthesized fluorinated antiferroelectric liquid crystal namely (S) 4-(1-methylheptyloxycarbonyl) biphenyl-4′-yl-4-[6-(tridecafluoro heptanoyloxy)hexan-1-oxy]benzene-1-carboxylate (6F6B) in its planar orientation has been carried out. 6F6B shows a Cr→SmCA*↔SmC*↔SmA*↔I phase sequence. It shows five different modes of dielectric relaxations in different phase. In SmA* phase, relaxation frequencies of usual soft mode are temperature dependent and decreases with decrease in the temperature. Dielectric strength is small but increases with decrease in the temperature and follows Curie Weiss’ law. Ferro-electric SmC* phase shows Goldstone mode having large dielectric strength in the low-frequency region. Its relaxation frequencies are almost invariant with the temperature. It has been possible to completely suppress Goldstone mode by applying DC bias. Three modes of dielectric relaxation have been clearly observed in antiferro-electric SmCA* phase, each of them separated by about two decades of frequency. Two modes are due to the in-phase and anti-phase azimuthal angle fluctuation of the anti tilt pairs of the molecular directors, respectively, whereas the third one is due to ionic conductance, which is common in all phases.