Temperature-induced helix inversion in naphthyl-based cholesteric liquid crystals

Abstract

Achieving precise control over macroscopic chirality in self-organized systems is a key challenge in the development of advanced supramolecular functional materials. Here, we report a novel class of liquid crystalline compounds bearing a single chiral center, which exhibit reversible, thermally-induced helix inversion in the cholesteric phase. The (S)-naphthyl-3-hydroxypropanoic moiety is identified as the critical structural fragment responsible for this rare behavior. Remarkably, the helix inversion can be transferred from the pure chiral compound to an achiral nematic host, at guest concentrations as low as 6%, preserving the characteristic transition from a high-temperature left-handed helix to a low-temperature right-handed one. This also enables precise tuning of the helix inversion temperature across an exceptionally broad range – from below room temperature up to 114 °C. Importantly, structural modifications to the alkyl ester moiety do not suppress helix inversion, allowing for targeted tuning of inversion temperature, host compatibility, and potential incorporation of additional stimuli-responsive functions. The combination of thermally-induced helix inversion, the ability to transfer this unique feature to an achiral host, and the wide temperature range over which this inversion can be adjusted makes these new chiral mesogens a versatile molecular platform for designing thermoresponsive chiral materials.