Tunable Structural Colors via Liquid Crystal Elastomers with Oblique Helicoidal Structures

Abstract

Structural colors, abundant in nature, have attracted enormous attention owing to high hues and time-independent characteristics. Cholesteric liquid crystals (CLCs) that produce selective Bragg reflection are promising candidates for structural colors. Nevertheless, due to intrinsic molecular orientation, CLC-based structural colors have limitations on wide bandwidth (i.e. low color purity) and narrow color tuning range. Here, we propose oblique helicoidal cholesteric (ChOH) elastomer that shows tunable structural colors with narrow bandwidth. Specifically, we prepare ChOH elastomer by employing polymerizable mesogen and oligomer on ChOH exhibiting selective Bragg reflection with narrow bandwidth from ultraviolet to infrared. The polymerizable mesogens align along the ChOH molecules, thus enabling oblique helicoidal structures to be stabilized by photopolymerization and providing ChOH elastomer that maintains selective Bragg reflection of ChOH. Furthermore, the reflection wavelength of the ChOH elastomer can be modulated by temperature and mechanical stress. This work was supported by the NRF (2021R1A2C2095010 and 2022M3C1A3081312).