Electrochromic Triarylamine-Based Polyamides and Their Application in Intelligent Color-Varying Windows

Polyamide (PA) is a classical conductive polymer that has become a research hotspot in the field of electrochromism due to its easily modifiable structures, tunable absorption spectra, and superior film-forming properties. Herein, four PAs are successfully synthesized, including C4-PA, C7-PA, C9-PA, and TP-PA, to study their thermal, photophysical, electrochemical, and electrochromic properties. All four PAs exhibit good thermal stability and excellent solubility in the volatile solvent THF. The fluorescence intensity follows the trend of C9-PA > C7-PA > C4-PA = TP-PA. Notably, C4-PA, C7-PA, C9-PA, and TP-PA-based electrochromic devices (ECDs) exhibit reversible electrochromism from transparent to pure black, blue-black, blue-green, and turquoise colors, respectively. Especially, C4-PA demonstrate high contrast (70%), fast response time (coloring time of 3.1 s and fading time of 2.7 s), and pure black color (the lowest contrast < 1%) in the colored state ((a*, b*) = (-1.82, -0.39) in ECD. However, C7-PA, C9-PA, and TP-PA based ECDs exhibit longer response times and only demonstrate the lowest contrast of 6%, 22%, and 36% in the colored state, respectively. To achieve high contrast and fast response times, it is suggested to use shorter carbon chains in the design of PA-based EC materials.