Phase changing poly(ionic liquid) with electrolytic functionality for a single-layer ionogel-based smart window with multi-stimuli response

Abstract

Functional materials play a crucial role in the design of smart windows that can provide a more comfortable indoor environment for people to enjoy a better lifestyle. A traditional smart window material tends to have only a single feature wherein the color change is led by solar energy input. It was known that different color tones have a significant influence on people's emotions. Herein, our group has adopted a strategy to combine the properties of an electro- and thermo-chromic in a single layer (all-in-one) ionogel. In this work, 3-chloro-N-isopropylacetamide containing thermo-responsive poly [VNIm][TFSI] based electroactive has been synthesized for multi-responsive device. Ionogel, consisting of MBV [TFSI], ferrocene, and poly [VNIm][TFSI], was utilized to construct a single layer (all-in-one) device (with and without water). The proposed ionogel based device 1 (with water) that could offer a useful response to surrounding environments by switching between opaque and transparent in the aqueous condition through a temperature change. This kind of device 1 can be utilized as an individual privacy smart windows, under specific conditions. On the other hand, the ionogel based device 2 (without water) exhibits remarkable electrochromic performance through a reversible color change between colorless to purple color once 1.8 V was applied at 25 °C (below UCST) and gave a high (ΔT) of 74.9% and a coloration efficiency (CE) of 229.03 cm2 C−1 with coloration and bleaching times of 10.2 s and 100 s, respectively, while the tone changes from purple to blue when the device 2 is above UCST (52 °C). These phenomena are caused by the synergetic effect of its electrochromic reaction and thermochromic behavior. The device 2 maintained its switching stability for >2000 cycles. This novel strategy of integrating thermo- and electrochromic materials into a single device will lead to the development of the next generation of multifunctional smart windows.