Nematic and Smectic Phases with Proper Ferroelectric Order.

A material showing a sequence of three ferroelectric liquid crystalline phases below the paraelectric nematic phase is synthesized and studied. The polar order of molecules appearing due to the dipole-dipole interactions in the ferroelectric nematic, N, phase is preserved also in the smectic phases: orthogonal SmA and tilted SmC. The ferroelectric ground state of both smectic phases is confirmed by their second harmonic generation (SHG) activity and polarization switching.

Polar Order in a Fluid Like Ferroelectric with a Tilted Lamellar Structure - Observation of a Polar Smectic C (SmC) Phase.

The discovery of fluid states of matter with spontaneous bulk polar order is appreciated as a major discovery in the fields of soft matter and liquid crystals. Typically, this manifests as polar order superimposed atop conventional phase structures and is thus far limited to orthogonal phase types. Here we report a family of materials which exhibit a previously unseen state of matter which we conclude is a polar smectic C phase, and so we term it SmC.

Spontaneous chiral symmetry breaking in polar fluid-heliconical ferroelectric nematic phase.

Spontaneous mirror symmetry breaking by formation of chiral structures from achiral building blocks and emergent polar order are phenomena rarely observed in fluids. Separately, they have both been found in certain nematic liquid crystalline phases; however, they have never been observed simultaneously. Here, we report a heliconical arrangement of achiral molecules in the ferroelectric nematic phase.

Ferroelectric Nematic-Isotropic Liquid Critical End Point.

A critical end point above which an isotropic phase continuously evolves into a polar (ferroelectric) nematic phase with an increasing electric field is found in a ferroelectric nematic liquid crystalline material. The critical end point is approximately 30 K above the zero-field transition temperature from the isotropic to nematic phase and at an electric field of the order of 10  V/μm. Such systems are interesting from the application point of view because a strong birefringence can be induced in a broad temperature range in an optically isotropic phase.

Chiral columns forming a lattice with a giant unit cell.

Mesogenic materials, quinoxaline derivatives with semi-flexible cores, are reported to form a new type of 3D columnar phase with a large crystallographic unit cell and lattice below the columnar hexagonal phase. The 3D columnar structure is a result of frustration imposed by the arrangement of helical columns of opposite chiralities into a triangular lattice. The studied materials exhibit fluorescence properties that could be easily tuned by modification of the molecular structure; for compounds with the extended π electron conjugated systems the fluorescence is quenched.