Multi-responsive thiazolothiazole viologen-based electrochromic materials for smart windows and electronic displays

Viologen derivatives have emerged as key players in electrochromic materials due to their excellent optical and electrical properties. They show great promise for application in smart windows, electronic displays, and flexible sensors. In this study, we synthesized a novel thiazolothiazole viologen derivative (TZ-DAV) with diallyl functional groups and integrated it with N-isopropylacrylamide to create multi-stimuli responsive electrochromic polymers (P-NIPAM-TZ-BMIm and P-NIPAM-TZ-BVIm). These polymeric materials are sensitive to electric fields and respond to environmental stimuli such as temperature changes. Remarkably, P-NIPAM-TZ-BMIm and P-NIPAM-TZ-BVIm exhibit thermo-responsiveness behavior within the temperature range of 24-40 °C, resulting in a transmittance change from approximately 93% to 2%. Additionally, the incorporation of imidazolium ionic liquids enables us to fine-tune the critical response temperature of the polymer, enhancing its adaptability for various environmental applications. For smart window applications, these materials can intelligently adjust indoor lighting and temperature in response to environmental changes within the range of 33.5 to 39 °C, thereby offering significant energy-saving benefits. In the field of electronic display technology, materials with a low color change voltage exhibit high-contrast color display capabilities within 1–3 s at a voltage of 2.7 V. Particularly at a wavelength of 632 nm, there is a significant enhancement in absorbance. Moreover, these materials exhibit fluorescence quenching at 460 nm, coupled with a fluorescence quantum yield reaching up to 91.0%. These attributes are supportive of the development of next-generation high-performance display devices.