Porous membranes of recycled poly(ethylene terephthalate) (PET) were prepared by nonsolvent-induced phase separation (NIPS) and evaluated for the first time for the filtration in high temperature solvents and other harsh environments. The PET was recycled from commercial water bottles. The morphology, pore size, and pore density were optimized by varying the composition of the polymer concentration in the casting solution, the solvent, and the nonsolvent bath in conditions of controlled humidity and temperature. Poly(ethylene glycol) (PEG) of 0.2 and 1 kg mol–1 was used as an additive and pore inducing agent. The filtration performance of the membranes was tested under different solvents and temperatures. The obtained PET membranes were successfully applied for ultrafiltration with a MWCO of 40 kg mol–1 in dimethylformamide (DMF) at temperatures up to 100 °C. PET membranes were found to be resistant to a wide variety of solvents as well as in chlorine and acid medium. They could be used as porous support for thin-film composite membranes and for different applications requiring high chemical and heat resistance.
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 (M n) 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).
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