Solvent Response and Protonation Effects of Novel Aramides Containing Pyridine and Unsymmetrical Carbazole Moieties

A new diamine containing pyridine and carbazole groups was synthesized via a Chichibabin reaction and subsequent reduction; this compound was then used in the preparation of organo-soluble aramides ( PA-a–i ). The resultant polymers had high glass transition temperatures, which fell within the ranges of 271–287 °C, and T d10 at 510–535 °C in a nitrogen atmosphere. The pristine PA-a exhibited the maximum value in the UV–vis absorption spectrum at 307 nm, and this value shifted to 394 nm after protonation by HCl. When the emission of the polymer in THF solution was observed, the intensity of the emission peak at 420 nm decreased and the intensity of a new emission peak at 552 nm increased as the acid concentration increased. Additionally, the color of the polymer solution changed from blue to yellow after protonation. The intensity of the emission at 552 nm based on excimers increased as MeOH content increased. The color of polymer films also changed irreversibly from yellow, which was indicative of the neutral form, to a dark brown oxidized form during the application of bias voltages ranging from 0 to 1.6 V.