Polar response and Fréedericksz transition in cybotactic nematic fluids of unsymmetrical bent-core molecules

Abstract

The appearance of polar order in nematic fluids is of broad interest rejuvenating affluent concepts of physics and chemistry. In bent-core nematics (BCNs), ferroelectric switching is a challenging quest of considerable interest after its primary observation in 1,2,4-oxadiazole-based BCNs. Herein, we observed induced polar switching in the cybotactic nematic phase (Ncyb) with a polarization value of ∼185 nC/cm2 in an unsymmetrical bent-core compound 8-F-OH. Temperature-dependent SAXS/WAXS analysis and dielectric measurements revealed nano-sized cybotactic clustering within the nematic phase. Electric-field-induced Fréedericksz transitions (FT) in the Ncyb phase at different frequencies and temperatures were investigated. Compound 8-F-OH exhibited two domains that formed and competed when the system was driven by an ac field. Thus, the build-up process of FT involved the reorientation of molecules and the transport of domains, where each had a distinctive characteristic time. We envisage that these detailed investigations can pave a bright way toward the development of advanced-level optical and electro-optical applications of BCN systems.