Planar or not planar is A problem. Electrochromic polyamides with The monomer containing dibenzofluorene fused to triphenylamine for smart windows with high contrast ratio aimed for energy conservation

Abstract

According to requirement of energy conservation and environmental protection, electrochromic (EC) smart windows have been widespread implemented in building recently. However, there is challenge to tackle short life time and instability. During the EC smart windows (ESW) operation, as the electrolyte ions insert and detach from the EC film, the film will swell and shrink resulting in the collapse of the film. The molecules having planar part together with some twisted modification will take effect. Therefore, diphenylfluorene fused with triphenylamine (TPA) monomer is designed, followed by a series of polyamides (PAs) having been synthesized by polycondensation from the monomer and four dicarboxylic acids which exhibit superior solubility in polar solvents facile to form films. The solubility is mainly contributed to two benzene rings at the C9 position of the fluorene group, together with the two bulky TPA, which provide more pathways for the penetration of counter ions. The core fluorene moiety provides appropriate aggregate between mainchain resulting in the fast electrons hopping from polymer chain to conductive substrate. The polymer film (named DPFTPA-OA) exhibits 79 % transmittance change at 520 nm, as well as fast and stable EC behaviors (coloring/bleaching times of 2.2 s/1.3 s, and 1200 cycles of stabilization). Based on the superior voltage-controlled solar modulation capability of DPFTPA-OA, EnergyPlus simulation demonstrates that ESWs assembled with DPFTPA-OA by optimizing radiant heat exchange between indoor and outdoor environments in most China cities, have higher energy savings compared to commercial standard glass, so it exhibits considerable potential for energy management. In addition, DPFTPA-CA shows PL sensitive to 2,4,6-trinitrophenol (TNP) with K_sv = 2.2 × 10⁵ M^-1 and LOD = 43 nM, exhibiting great potential in environmental hazard test.