Electric-Field-Induced Chirality in Columnar Liquid Crystals

Abstract

We describe a novel class of tetraphenylbenzene-based discotic molecules with exceptional self-assembling properties. Absorption and fluorescence studies confirmed the formation of Jtype aggregates in solution. The discotic mesogens also show an enhancement of the emission upon aggregation. Interestingly, these discotic molecules displayed enantiotropic hexagonal columnar liquid crystal (LC) phases that can be switched into a helical columnar organization by application of an electric field. The helical columns arise from the electric-field-induced tilt of the polar fluorobenzene ring that directs all of the peripheral phenyl groups into a propeller-like conformation with respect to the central benzene core. A cooperative assembly process of these propeller-shaped molecules resolves into a helical columnar organization, in which the preferred helical sense is obtained from the stereogenic center proximate to the polar carbon−fluorine bond. The ease of inducing chirality in columnar LCs by an electric field presents opportunities to create nextgeneration chiral materials for a variety of applications.

Molecular Shape and Polar Order in Columnar Liquid Crystals

“…The polar chains are along the polymer axis and can be polarized and switched by application of electric f ields. • Xu, B.; Swager, T. M. Rigid Bowlic Liquid Crystals Based on Tungsten-Oxo Calix [4]arenes: Host-Guest Effects and Head-to-Tail Organization J. Am.…”

“…2021, 143, 9260−9266. 4 Building on our propeller concepts, we found that materials could be made that were too dynamic to resolve spontaneously. However, by applying electric f ields along the column axes we induce chirality in the conformations of the aromatic mesogenic cores.…”

“…25 These shapes can only pack efficiently when organized in a headto-tail structure and therefore cause polar order within a column. To create bowlic LC materials with large dipoles and potentially useful chromophores, we designed W�O calix [4]arene complexes. 2 Similar to the vanadyls, the position trans to the W�O bond is Lewis acidic, and these systems display a wealth of host−guest chemistry with donor ligands.…”

“…26 We isolated the LCs with DMF guest molecules bound in the bowlic cavity, which promotes low-temperature melting and evaporation of the guests produced a LC Col H phase (Figure 10). The same metal-free calix [4]arene compounds showed unusual LC behavior and melt into a bowlic Col H phase, but once in the isotropic phase, a mixture of conformations is generated that prevents reforming of the Col H phase with cooling. We found that adding small molecule diamides promotes a host−guest bowlic conformer and generated a stable Col H phase.…”

Selectively Regulating the Chiral Morphology of Amino Acid-Assisted Chiral Gold Nanoparticles with Circularly Polarized Light

“…Commonly used chiral inducers are helical self-assembly scaffolds, cholesteric liquid crystal compounds, and chiral biomolecules (especially, amino acids, peptides, and DNA), and these can be used to synthesize different kinds of chiral nanostructures. ,− The other strategy is the photon-to-matter chirality transfer. This method fabricates chiral nanomaterials that possess specific optical or magnetic properties by applying external driving forces, such as an electric field, magnetic field, or circularly polarized (CP) light. − Compared to the traditional chemistry-driven chirality transfer, utilizing the physical light–matter interaction properties of plasmonic material has opened up a novel opportunity for synthesizing chiral nanostructures by CP light. This is becoming a promising research direction due to the dependence on the transfer of spin angular momenta .…”