Electrochemical behavior of N,N,N′,N′-tetraphenyl-1,4-phenylenediamine moiety on novel aromatic polyamides and their electrochromic properties

A series of novel aromatic polyamides with N,N,N′,N′-tetraphenyl-1,4-phenylenediamine units were prepared from the diamine, N,N′-bis(4-aminophenyl)-N,N′-diphenyl-1,4-phenylenediamine, and various aromatic dicarboxylic acids via the direct phosphorylation polycondensation. All the polyamides were amorphous, readily soluble in many organic solvents and could be solution cast into transparent, tough, and flexible films with good mechanical properties. They had useful levels of thermal stability associated with relatively high glass-transition temperatures (257–287 °C). These polymers exhibited strong UV–vis absorption bands with a maximum at 320–336 nm in NMP solution. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms (CV) of these films prepared by casting polymer solution onto an indium-tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at potentials 0.61–0.64 and 0.99–1.07 V, respectively, vs Ag/AgCl in acetonitrile solution. All obtained polyamides revealed excellent stability of electrochromic characteristics, changing color from original pale yellowish to green, and then to blue at electrode potentials 0.65 and 1.10 V, respectively.