Tuning the main electrochromic features by polymer backbone variation of triphenylamine-based polyamides

A novel triphenylamine (TPA)-based diamine integrating structural elements to endow highly stable redox and electrochromic features was successfully synthesized and structurally characterized. Three new TPA-containing polyamides were obtained via polycondensation of this diamine with acid dichlorides, as confirmed by thorough NMR and FT–IR investigations. The main electronic transitions and specific oxidation sites were evaluated by photo-optical and (time-dependent) density functional theory ((TD)– DFT) analysis, respectively. Cyclic voltammetry and spectroelectrochemical investigations were used to assess the redox stability and to comprehend the electrochromic conduct in terms of electrochromic contrast, response time, and switching stability. Thus, the synthesized polyamides integrated high transmittance variation up to 67%, response time to coloring and blanching down to 6.52 s/2.01 s, a maximum of 219 cm2/C of the electrochromic efficiency (EC) and a decay up to 5% after 500 cycles. All these electrochromic parameters and their variation are contingent to the electronic effect of each acid dichloride segment from the polymers. Also, the presence of the ortho-catenated methyl groups lowered the overall oxidation potentials and therefore triggered long-term stability. Computational evaluations were used to endorse practical assessments. All experimental and theoretical observations were subjected to interconnected reasoning to determine the correlations between structural motifs and resulting electrochromic performances.