Electrochromic properties of novel strictly alternating poly(amine–amide–imide)s with electroactive triphenylamine moieties

A series of novel triphenylamine-containing aromatic poly(amine–amide–imide)s (PAAIs) were prepared by the phosphorylation polyamidation reactions from the diamine, N,N′-bis(4-aminophenyl)-N,N′-diphenyl-1,4-phenylenediamine, and various imide ring-preformed dicarboxylic acids. All the PAAIs were amorphous, had good solubility in many polar aprotic solvents, and exhibited excellent thin film forming capability with good mechanical properties. They displayed relatively high glass-transition temperatures (220–306 °C) and good thermal stability, with 10% weight-loss temperatures in excess of 522 °C in air or nitrogen and char yields at 800 °C in nitrogen higher than 66%. 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 0.63 and 1.01 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.