Self-bleaching dual responsive poly(ionic liquid) with optical bistability toward climate-adaptable solar modulation

Abstract In the development of smart windows, functional polymer materials play a crucial role, which can provide a more comfortable indoor environment for people to enjoy a better lifestyle. However, many of the implied smart windows that have been studied to date respond to only one stimulus, but studies on dual-responsive smart windows have been increasing. The growing interest in multi-responsive smart windows is due to the many opportunities in terms of utility and activity that they offer. Herein, our group has adopted a strategy to combine the thermo- and electro-chromic as well as electrolyte properties in one single molecule. Dual-responsive poly(ionic liquid) (PIL) 6 based electrolyte was synthesized via radical polymerization of poly(ethylene glycol) diacrylate (PEGDA) with N-isopropylacrylamide (NIPAM) with viologen based electroactive monomer utilizing AIBN as an initiator in DMSO. One single molecule (all-in-one) single-layer device consisting of ITO/smart PIL/ITO was assembled on a glass substrate, that can enhance its optical efficiency and characteristics of phase shift. The proposed electrochromic device exhibits tunable transparency and electrochromic properties due to the thermo-responsive property of PNIPAM and the bistable electrochromic property of a viologen-based electroactive monomer, respectively. Consequently, the acquired dual-responsive properties of smart PIL 6 for the development of bistability smart windows can not only control solar energy input but can also provide a more comfortable color tone to boost people's feelings and emotions in indoor environments.