Amplitude and phase fluctuation modes of a newly synthesized anti ferroelectric liquid crystal material 4F6Bi

Frequency and temperature dependent dielectric spectroscopy of a newly synthesized anti ferroelectric liquid crystal (AFLC) material namely “(S)-(+)-(1-methylheptyloxycarbonyl)phenyl 4′-(6-perfluoropentanoyloxyhex-1-oxy) biphenyl-4-carboxylate ((S) (4F6Bi))” has been carried out in the frequency range 1 Hz to 1 MHz under planar anchoring conditions of the molecules. 4F6Bi possesses paraelectric (SmA⁎), ferroelectrics (SmC⁎), and wide range anti ferroelectric (SmCA⁎) phases. The SmA⁎ phase shows soft mode relaxation related with the tilt fluctuations. Its relaxation frequencies are highly temperature dependent and decreases with decrease in the temperature. Dielectric strength is small (~ 1.0-2.5) but increases with decrease in temperature and follows Curie-Weiss' law. The SmC⁎ phase shows Goldstone mode with its dielectric strength slowly increasing with decreases in the temperature, and shows maximum value (~ 64) just above the SmC⁎-SmCA⁎ transition at 118.1 °C. Goldstone mode relaxation frequency has been found to be almost invariant with temperature (~ 3.5 kHz). Two modes of dielectric relaxation have been observed in the SmCA⁎ phase due to anti ferroelectric ordering of molecules.