Synthesis, luminescence and electrochromism of aromatic poly(amine-amide)s with pendent triphenylamine moieties

A new triphenylamine-containing aromatic dicarboxylic acid monomer, N,N- bis(4-carboxyphenyl)-N',N'-diphenyl-1,4-phenylenediamine ( 2), was synthesized from the amination reaction between 4-aminotriphenylamine and 4-fluorobenzonitrile and subsequent alkaline hydrolysis of the dinitrile intermediate. A series of novel aromatic poly(amine-amide)s with triphenylamine units in the main chain and as the pendent group were prepared from the newly synthesized dicarboxylic acid and various aromatic diamines. These poly(amine-amide) s were amorphous and readily soluble in many organic solvents. All the polymers could be solution-cast into flexible films with good mechanical properties. They had excellent levels of thermal stability associated with high glass-transition temperatures (226-261 degrees C). These polymers exhibited strong UV-vis absorption bands at 350-365 nm in NMP solution. Their photoluminescence spectra showed maximum bands around 512-543 nm in the green region. The hole-transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine-amide) 5a prepared from the dicarboxylic acid monomer 2 with a structurally similar diamine monomer N, N- bis(4-aminophenyl)-N',N'-diphenyl-1,4-phenylenediamine (4a) exhibited four reversible oxidation redox couples in acetonitrile solution at E-1/2 = 5 0.60, 0.80, 0.97 and 1.13 V, respectively. All the poly(amine-amide)s exhibited excellent reversibility of electrochromic characteristics by continuous five cyclic scans between 0.0 to 1.30 V, with a color change from the original pale yellowish neutral form to the green and then to blue oxidized forms.