Multiple ferroelectric nematic phases of a highly polar liquid crystal compound

Abstract

Ferroelectric nematic liquid crystals represent not only interesting fundamental science, but they also hold promise for storage capacitors with high power density or new information display technology having sub-millisecond switching. In this work we describe the synthesis and measurements of the physical properties of a new highly polar ferroelectric nematic compound, 4-nitrophenyl 4-[(2,4-dimethoxylbenzoyl)oxy]-2-fluorobenzoate (RT11001). The dipole moment of this material (along the long molecular axis) is calculated to exceed 11.5 Debye. We employ a wide range of physical characterization methods including differential scanning calorimetry (DSC), mass density measurement, optical birefringence, polarizing optical microscopy (POM), electric current analysis, and electro-optical switching, to show that RT11001 has three distinct ferroelectric states, F1, F2 and F3. F1 is purely orientationally ordered ferroelectric nematic phase (NF), F2 has a ferroelectric nematic with possibly short-range hexagonal order normal to the director (NhF), and we conjecture that F3 has a long-range hexagonal order normal to the director (ColhF).