Electroconvection in Zwitterion-Doped Nematic Liquid Crystals and Application as Smart Windows

Electroconvection (EC) in liquid crystals (LCs) is extensively studied for the formation of regular nonequilibrium structures, and the applications that require strong light scattering and high haze. Doping the LCs with ionic species has proven to be an effective method to obtain uniform and high-quality textures. Herein, zwitterion is explored as a new class of ionic dopant that has little problem of ion accumulation as compared to typical organic electrolytes. A rich variety of EC patterns are observed and characterized for both positive and negative LCs doped with a zwitterion Reichardt's dye. The initial homogeneous or homeotropic alignment, as well as the voltage and frequency of the applied electric field, is shown to influence the formation of EC patterns, among which the dynamic scattering mode (DSM) is specially examined for the application as privacy-protecting smart windows. Using an LC mixture doped with zwitterions, the smart window demonstrates outstanding performance, as well as much improved durability for a wide range of operating conditions. Such a method offers a simple strategy for the fabrication of polymer-free smart windows.