Synthesis and characterization of the first perfluoroaromatic polyimide of the AB-type

Aminodefluorination of tetrafluorophthalic acid by anhydrous ammonia was shown to give 4-amino-3,5,6-trifluorophthalic acid selectively and in a high yield. Under the action of dicyclohexylcarbodiimide this acid was quantitatively converted into 4-amino-3,5,6-trifluorophthalic anhydride, which is the simplest monomer of the AB-type. The first perfluoroaromatic AB-type polyimide was prepared by the one-step high-temperature polycondensation in a benzoic acid melt and characterized using FTIR, NMR, UV–vis, MALDI TOF MS, and TG/DSC methods. The near-IR spectrum of the polyimide exhibits no absorption of C–H and O–H bond harmonic vibrations, which testifies to considerable promise of AB-type perfluorinated polyimides for optical communication systems.