Novel electrochromic aromatic poly(amine–amide–imide)s with pendent triphenylamine structures

Three new aromatic poly(amine–amide–imide)s (PAAIs) having pendent triphenylamine units were prepared from the phosphorylation polyamidation reactions of a newly synthesized diamine, N,N-bis(4-aminophenyl)-N′,N′-diphenyl-1,4-phenylenediamine, with three imide ring-preformed dicarboxylic acids. These PAAIs had inherent viscosities of 0.54–0.86 dL/g, and they were amorphous and readily soluble in many organic solvents and could be solution cast into transparent, tough, and flexible films with good mechanical properties. They displayed relatively high glass-transition temperatures (279–287 °C) and good thermal stability, with 10% weight-loss temperatures in excess of 522 °C in nitrogen and char yields at 800 °C in nitrogen higher than 67%. The solutions of polymers in NMP exhibited strong UV–vis absorption bands with a maximum around 315 nm. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the PAAIs prepared by casting polymer solution onto an indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at 0.67 and 1.08 V vs. Ag/AgCl in acetonitrile solution. All the PAAIs revealed very stable electrochromic characteristics, changing color from original pale brownish to green, and then to blue at 0.67 and 1.08 V, respectively.