Electrochemical and electrochromic studies of redox-active aromatic polyamides with 3,5-dimethyltriphenylamine units

• 3,5-Dimethyltriphenylamine-based diamine and diacid monomers were synthesized.
• Redox-active and electrochromic polyamides with 3,5-dimethylTPA units were prepared.
• Orientation of amide linkage on the properties of the polyamides was also studied.

New triphenylamine-based aromatic diamine and dicarboxylic acid monomers, namely 3,5-dimethyl-4′,4″-diaminotriphenylamine (3a) and 3,5-dimethyl-4′,4″-dicarboxytriphenylamine (3b), were successfully synthesized by well-established procedures. Two series of novel aromatic polyamides 5a–5h and 7a–7e with 3,5-dimethyltriphenylamine units were prepared respectively from phosphorylation condensation of 3a with commercially available aromatic dicarboxylic acids and from 3b with commercially available aromatic diamines. Almost all the polyamides were amorphous and could be solution-cast into flexible, transparent, and tough films. All the polyamides exhibited useful levels of thermal stability, such as high glass-transition temperatures of 245–322 °C, 10% weight-loss temperatures in excess of 500 °C, and char yields at 800 °C in nitrogen higher than 63%. Cyclic voltammograms of the 5 series polyamides exhibited a reversible oxidation wave with E1/2 around 0.95 V versus Ag/AgCl in acetonitrile solution. The polymer films revealed excellent stability of electrochromic characteristics, with a color change from neutral state pale yellowish to green doped form at applied potentials ranging from 0 to 1.25 V.

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