Synthesis and characterization of novel electrochromic poly(amide-imide)s with N,N′-di(4-methoxyphenyl)-N,N′-diphenyl-p-phenylenediamine units

Abstract

We developed a new efficient procedure for the synthesis of a bistriphenylamine diamine monomer, N,N′-bis(4-aminophenyl)-N,N′-bis(4-methoxyphenyl)-1,4-phenylenediamine (3). A new dicarboxylic acid monomer bearing two built-in imide rings, namely N,N′-bis(trimellitimidophenyl)-N,N′-bis(4-methoxyphenyl)-1,4-phenylenediamine (4), was synthesized from the condensation of diamine 3 with two equivalent amounts of trimellitic anhydride. Several novel electroactive poly(amide-imide)s (PAIs) containing N,N′-di(4-methoxyphenyl)-N,N′-diphenyl-p-phenylenediamine [TPPA(OMe)₂] units have been prepared by the phosphorylation polyamidation reactions from diamine 3 with four imide ring-preformed dicarboxylic acids or from diimide-diacid 4 with 4,4′-oxydianiline and diamine 3, respectively. All the PAIs were readily soluble in many organic solvents and could be solution-cast into tough and flexible polymer films. These PAIs exhibited glass-transition temperatures (T_gs) in the range 206–292 °C, and most of them did not show significant weight-loss before 450 °C. The PAI films revealed reversible electrochemical oxidation processes accompanied with strong color changes from the pale yellow neutral state to yellowish green and deep blue oxidized. Incorporating the TPPA(OMe)₂ unit on the amide side of PAIs led to lower oxidation potentials and higher redox and electrochromic stability.