Rational Design, Synthesis and Characterization of Fluorinated Cyano-Terminated Diester Liquid Crystals Exhibiting...

The discovery of the ferroelectric nematic (N_F) phase has attracted significant attention from the soft matter community, both for exploring the scientific basis of its origin and for advancing its potential applications in devices such as optical modulators and high-energy-density storage supercapacitors. Unlike rigid solid-state ferroelectrics, the fluidic nature of N_F materials offers additional flexibility in device fabrication. In the N_F phase, these materials exhibit remarkably large saturated spontaneous polarization (≳6 μC/cm²), which is comparable to that of the solid-state ferroelectrics, and consequently, these materials will exhibit exceptionally strong nonlinear electro-optic effects. In this paper, we report the synthesis of three new N_F phase compounds with an extended temperature range of up to 103 °C. Two of these compounds show a direct Iso-to-N_F phase transition, and in two cases, a monotropic N_F phase was observed below 30 °C. The design and synthesis of the materials are described. The compounds are characterized by analysis of textures using polarizing optical microscopy. X-ray measurements show that the effective length of the molecule is smaller in the N_F phase than in the N/Iso phase seemingly arising from a better orientational ordering of the polar molecules. Dielectric measurements confirm the presence of a ferroelectric mode of large dielectric strength in the N_F phase. Temperature-dependent birefringence data show a large increase in the order parameter at the Iso-N_F or N-N_F transition temperature. The fundamental properties determined for these materials will support their future applications.