Eaton’s reagent in polybenzimidazole synthesis

The polycondensations of 3,3′-diaminobenzidine with two acids, 4,4′-oxybis(benzoic acid) and hexafluoroisopropylidene bis(benzoic acid), were conducted in Eaton’s reagent at the unusually high temperature of 180°C and under microwave irradiation at 90°C. Both protocols resulted in soluble polybenzimidazoles, OPBI and CF 3 PBI, of high molecular weights in very short reaction times. The synthesized polybenzimidazoles exhibited high thermostability and excellent mechanical properties. The influence of the reaction conditions on the polymer structure and molecular weights was studied. The “microwave effect” was demonstrated by comparison of the polycondensations conducted under microwave irradiation and conventional heating.