Control of structural color of chiral nematic liquid crystal dimers

Abstract

A liquid crystalline dimer consisting of two cholesteryl moieties linked with nitrophenylene was synthesized. The dimer compound exhibited a chiral nematic liquid crystal phase and its reflective light shifted over a wide wavelength range from red to blue in response to slight temperature changes. The wavelength shift of this chiral nematic compound with respect to temperature was opposite to that of the general chiral nematic compound. Additionally, applying a horizontal voltage caused a change in color tones from red to green. Its phase transition behavior, liquid crystallinity, and reflected light behavior were investigated using polarized optical microscopy (POM), differential scanning calorimetry (DSC), one- and two-dimensional X-ray diffraction (1D-XRD and 2D-XRD), and microscopic reflection spectroscopy.