Influence of Bias on Dielectric Properties of Mesophases of a Laterally Fluorinated Antiferroelectric Liquid Crystal

Abstract

A laterally fluorinated antiferroelectric liquid crystal exhibiting SmA*, SmC* and SmC_A* phases was investigated using bias dependent dielectric spectroscopy. The critical field (Ec) for suppression of GM in SmC* phase was observed to increase with decrease of temperature. After suppression of Goldstone mode, domain mode (DM) arises at higher fields, the critical frequency (f _DM ) of which is ~10⁴ Hz and was recognized as surface domain mode. f_DM follows Arrhenius law. The activation energy (E_a) was found to be 19.8 kJ/mol. DM was also suppressed at high bias field. The weak low frequency P_L mode was not observed in SmC_A* phase instead a strong hereditary mode (HM) was observed in the low frequency region which also suppressed under dc bias field. The critical field for suppression of this mode was same at all temperatures. Variation of both $\upvarepsilon_{\text{HM}}^{{\prime \prime }}$ and f_SM within bias field 0.3 V/µm signifies that molecular dynamics of the mode is different from that of GM. The dielectric strength of soft mode ($\upvarepsilon_{\text{SM}}^{{\prime \prime }}$) converges and critical frequency (f_SM) diverges at T_c following the Curie-Weiss law.