One-Step, Room Temperature Synthesis of Well-Defined, Organo-Soluble Multifunctional Aromatic Polyimides

Efficient and ambient synthesis of aromatic polyimides (PIs) from readily available starting materials remains a very challenging task in polymer chemistry. Herein, we report for the first time a robust, one-step synthesis of organo-soluble functional aromatic PIs. Room temperature, metal-free, superacid (TFSA)-catalyzed step polymerization of aryl-terminated diimides with carbonyl compounds (2,2,2-trifluoroacetophenone and indoline-2,3-dione (isatin)) afforded 14 high-molecular-weight, linear, film-forming PIs. The effect of structural variation of the dianhydride segment, the amount of catalyst, and monomer concentration were studied. The PIs were obtained in quantitative yields, with high thermal stabilities up to 525 °C and 55% weight residue at 800 °C under an inert atmosphere and number-average molecular weights (Mn) in a range of 51–195 kg mol–1. Well-controlled proportions of the functional phenolic hydroxyl groups (at the ortho-position to the imide ring) and diaryloxindole reactive sites were introduced into macromolecules during polyimide syntheses, while pendent allyl and propargyl groups were formed by the chemical postpolymerization reactions. Subsequent modifications of the reactive sites using click-chemistry can afford multifunctional polymers with tunable properties. The thermal postpolymerization modification of polyhydroxyimides converts them into polybenzoxazoles (so-called thermally rearranged polymers).