Novel Aromatic Poly(Amine-Imide)s Bearing A Pendent Triphenylamine Group:  Synthesis, Thermal, Photophysical, Electrochemical, and Electrochromic Characteristics

A new triphenylamine-containing aromatic diamine, N,N-bis(4-aminophenyl)-N‘,N‘-diphenyl-1,4-phenylenediamine, was synthesized from the amination reaction between 4-aminotriphenylamine and 4-fluoronitrobenzene and subsequent reduction of the dinitro intermediate. A series of novel aromatic poly(amine-imide)s with pendent triphenylamine units were prepared from the newly synthesized diamine and various tetracarboxylic dianhydrides by either a one-step or a conventional two-step polymerization process. All the poly(amine-imide)s were amorphous and readily soluble in many organic solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide, and chloroform. These polymers 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 (264−352 °C), 10% weight-loss temperatures in excess of 568 °C, and char yields at 800 °C in nitrogen higher than 63%. These polymers exhibited strong UV−vis absorption bands at 311−330 nm in NMP solution. The photoluminescence spectra showed maximum bands around 545−562 nm in the green region. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-imide) films cast onto an indium−tin oxide (ITO)-coated glass substrate exhibited two reversible oxidation redox couples at 0.78 and 1.14 V versus Ag/AgCl in acetonitrile solution. The poly(amine-imide) films revealed excellent stability of electrochromic characteristics, with a color change from the pale yellowish neutral form to the green and blue oxidized forms at applied potentials ranging from 0.78 to 1.14 V.