Polarization-Dependent and Color-Tunable Electrochromic Smart Windows: Uniaxially Oriented and Polymer-Stabilized Viologen-Based Liquid Crystal Networks

Viologen-based reactive mesogen (VRM) is newly designed and synthesized for the development of polarization-dependent, color-tunable, and transparent electrochromic (EC) smart windows. By controlling electric field, the color of VRM can be intentionally tuned due to the formation of dication (D state), cation-radical (C state), and neutral state (N state). Based on the deep understanding of phase transition of VRM, a uniaxially oriented VRM hierarchical nanostructure is successfully constructed on the macroscopic area by simple coating and self-assembly processes. The subsequent photopolymerization significantly improves thermal, mechanical, and chemical stabilities of the VRM thin film. In addition to the control of color, the transmittance of uniaxially oriented VRM-based EC smart window can be precisely tuned by rotating a linear polarizer.