Mesomorphic and dielectric properties of strategically designed chiral bent-core liquid crystals displaying wide temperature range dark conglomerate phase

Abstract

In order to advance the scope of chiral functional materials, it is of paramount importance to engineer chiral bent-core liquid crystals (LCs) endowed with exceptional stability across a broad range of temperatures. In this context, we have devised a strategic approach, utilizing the potential of fluorinated molecules and taking advantage of the chirality of cholesterol as the pivotal component. This synergy has enabled the successful synthesis of our target LCs nF-4R. These molecules exhibit a chiral dark conglomerate (DC) phase over a broad temperature range of ∼85 °C in an enantiotropic manner. Dielectric spectroscopy measurements conducted on these materials showed persistent dielectric behavior over the entire LC range. Our study stands as a pioneering exemplar, unveiling the wide-range DC phase within the intricate landscape of chiral bent-shaped molecular systems. The mesomorphic characterization utilizing polarized optical microscopy, differential scanning calorimetry, and small-angle/wide-angle X-ray scattering measurements, revealed an optically isotropic DC phase. This phase shows domains of opposing chirality and belongs to the sponge-type DC phase. Notably, the enhancement of a specific chiral domain reveals the bias towards supramolecular chirality, attributable to molecular chirality as supported by circular dichroism measurements. This finding holds promise for chiral plasmonics, enantiomeric separation, and nano-templating applications.