Molecular Engineering for Chiroptical Smart Paints: Photo‐Tunable and Polymerizable Helical Nanostructures by Cyanostilbene‐Based Reactive Mesogens

Many studies on the basis of cholesteric liquid crystal (CLC) have focused on dynamic optical changes utilizing photochemical reactions raising helical pitch variations. However, the conventional dyes doped in CLC system often show reversible isomerization such as trans‐cis, E‐Z, and open‐close forms that hampers the fixation of desired color cues. Here, a cyanostilbene‐based reactive mesogen (CSRM) for phototunable and subsequently polymerizable smart CLC paints is newly designed and synthesized. The structural color of the CLC paint can be precisely manipulated in remote controllable manner by inducing a photochemical reaction of CSRM. Due to the irreversible isomerization behaviors of CSRM, the constructed periodic structures with different helical pitches are intactly fixed via in situ photopolymerization under 460 nm light. In addition, the combination of helical nanostructures and cyanostilbene luminophore produces a circularly polarized light emission. The dissymmetry factor of circularly polarized luminescence is dependent on the photoregulated helical nanostructures in CLC films. The decoupled system of triple photofunctionality in a single component of chirophotonic crystalline material is applied to develop advanced optical information storages. For photoregulatable and photopolymerizable smart cholesteric liquid crystal (CLC) paints, a cyanostilbene‐based reactive mesogen (CSRM) is newly synthesized and assembled with nematic and chiral monomers. The helical pitch and chiroptical properties are successfully controlled and fixed by the irreversible photoisomerization behavior of CSRM under UV light and photopolymerization with blue light. Utilizing the developed CLC paint, anti‐counterfeiting labels are demonstrated.