The multifunctional polyamides with triphenylamine-phenanthroimidazole-triphenylamine structure for electrochromic smart windows and specific chemical sensors

Electrochromic (EC) polymer materials have received increasing attention in recent years for the enormous potential of molecular customizability and multicomponent synergistic effects in the field of smart buildings and multifunctional optoelectronic materials. To develop multifunctional and superior optoelectronic materials, we have fabricated a diamine monomer (PIBTPA-A) with two EC units, triphenylamines (TPAs) and one photoluminescent unit, phenanthroimidazole (PI), and synthesized the corresponding redox-active polyamides (PAs). The PAs realized a dual-color EC change and a specific detection against ferric ions for multi-application directions. The twisted TPA and planar PI combined to enhance the charge transfer rate, which allowed the PA-OA film to exhibit dramatic electrochemical and EC properties, including fast switching times ( t c = 2.0 s and t b = 1.5 s) and the highest coloration efficiency ( η CE = 227 cm 2 /C), as well as cyclic switching at 12000 s with only 1.3 % decay. In addition, PA-CA based on the special recognition site of PI demonstrated specific detection against Fe 3+ with a limit of detection (LOD) of only 56 nM, while the emission of PA-CA and the presence of Förster resonance energy transfer (FRET) of the explosive 2,4,6-trinitrophenol (TNP) can be used for the ON-OFF type of sensors against the explosive TNP (LOD = 274 nM). Meanwhile, the electrochromic device (ECD) based on PA-OA demonstrates significant sunlight modulation capabilities, rendering it suitable for smart windows in buildings. Overall, the design of TPA-PI-TPA molecular structure provides a wider range of applications for multifunctional optoelectronic materials.