π-Extended Viologen-Based Lyotropic Chromonic Liquid Crystal Reactive Mesogen: Uniaxial Orientation and Photopolymerization for Transmittance and Color Controllable Electrochromic Smart Glass

To advance the development of an electrochromic (EC) smart glass, a π-extended viologen-based lyotropic chromonic liquid crystal (πV-LCLC) reactive mesogen (RM) is newly designed and successfully synthesized in this study. By extending the π-conjugation length of viologen, the πV-LCLC RM forms a stable LCLC phase at room temperature and retains its chemical integrity during the EC reactions, exhibiting reversible transitions across three redox states: dication (D), cation-radical (C), and neutral (N). A uniaxially oriented nanostructure is constructed on the macroscopic scale through shear-coating and molecular self-assembly. Subsequent photopolymerization of the uniaxially oriented πV-LCLC film significantly enhances its mechanical and chemical stability while enabling polarization-dependent transmittance and distinct color transitions. This newly developed πV-LCLC RM facilitates the fabrication of energy-efficient EC optical devices with tunable transmittance and multicolor modulation, and it is operable at a low voltage of 2.5 V.