Enhanced redox stability and electrochromic properties of aromatic polyamides based on N,N-bis(4-carboxyphenyl)-N′,N′-bis(4-tert- butylphenyl)-1,4-phenylenediamine

A new bis(triphenylamine)-type dicarboxylic acid monomer, N,N-bis(4-carboxyphenyl)-N′,N′-bis(4-tert-butylphenyl)-1, 4-phenylenediamine, was prepared by a well-established procedure and led to a new family of redox-active aromatic polyamides with di-tert-butyl-substituted N,N,N′,N′-tetraphenylphenylenediamine (TPPA) segments. The resulting polyamides were amorphous with good solubility in many organic solvents, and most of them could be solution cast into flexible polymer films. The polyamides exhibited high thermal stability with glass-transition temperatures in the range of 247-293 °C and 10% weight-loss temperatures in excess of 500 °C. They showed well-defined and reversible redox couples during oxidative scanning, with a strong color change from a colorless or pale yellowish neutral form to green and blue oxidized forms. They had enhanced redox stability and electrochromic performance when compared with the corresponding analogs without tert-butyl substituents on the TPPA unit. The polyamide with TPPA units in both the diacid and diamine components shows multicolored electrochromic behavior. A polyamide containing both the cathodic coloring anthraquinone chromophore and the anodic coloring TPPA chromophore has the ability to show red, green, and blue states, toward single-component RGB electrochromics.