Fluid Layered Ferroelectrics with Global C_∞v Symmetry

Abstract

Ferroelectricity in fluid materials, which allows free rotation of molecules, is an unusual phenomenon raising cutting‐edge questions in science. Conventional ferroelectric liquid crystals have been found in phases with low symmetry that permit the presence of spontaneous polarization. Recently, the discovery of ferroelectricity with high symmetry in the nematic phase has attracted considerable attention. However, the physical mechanism and molecular origin of ferroelectricity are poorly understood and a large domain of macroscopically oriented spontaneous polarization is difficult to fabricate in the ferroelectric nematic phase. This study reports new fluid layered ferroelectrics with the C∞v symmetry in which nearly complete orientation of the spontaneous polarization remains stable under zero electric field without any orientation treatment. These ferroelectrics are obtained by simplifying the molecular structure of a compound with a known ferroelectric nematic phase, although the simplification reduced the dipole moment. The results provide useful insights into the mechanism of ferroelectricity due to dipole–dipole interactions in molecular assemblies. The new ferroelectric materials are promising for a wide range of applications as soft ferroelectrics.

Emerging Ferroelectric Uniaxial Lamellar (Smectic AF) Fluids for Bistable In-Plane Polarization Memory

“…Here we design two highly rigid and fluorinated polar LC molecules with intrinsically large dipolar moment (>14 D) and introduce a new ferroelectric orthogonally lamellar LC phase, dubbed the ferroelectric smectic A (SmA F ) phase, right beneath the N F state (Figure ). Within the SmA F layers, the local polarization is along the long axis of molecules as similarly reported by Kikuchi et al and Chen et al very recently. It is revealed that the SmA F materials represent enhanced polarization properties, e.g., higher coercivity field ∼3.0 V μm –1 , remnant and saturated polarizations, i.e., ∼6.5 μC cm –2 , than the N F materials.…”

Synthesis of liquid crystals bearing 1,3-dioxane structures and characterization of their ferroelectricity in the nematic phase

“…1). 25 Therefore, it is necessary to evaluate the effect of structural variations on dipole moments, LC phases, and ferroelectricity in detail. Therefore, we synthesized various structured C3-DIO analogues, which are shown in Fig.…”

Nano-clustering mediates phase transitions in a diastereomerically-stabilized ferroelectric nematic system

“…Under this circumstance, the control of the phase sequences involving the N F emergence and the successful way of stabilizing N F remain ambiguous despite huge efforts on the design and development of new N F LC molecules based on molecular parameters. Note that a newfound ferroelectric state, that is, a uniaxial ferroelectric smectic A (SmA F ) phase 37,38 that appears just below the N F phase, just emerged, offering an important clue. SmA F looks highly correlated with the N F phase; hence, the smectic cluster floating in the N F media may influence the N F phase characteristic.…”