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A new diamine, 4-(4-trifluoromethylphenyl)-2,6-bis(4-aminophenyl)pyridine, was synthesized and used in the preparation of the fluorinated polyamides with inherent viscosities of 0.67–0.96 dL g−1 by direct polycondensation with aromatic dicarboxylic acids. The obtained polyamides have good solubility in many organic solvents such as N-methyl-2-pyrrolidinone, dimethylacetamide (DMAc), and tetrahydrofuran and exhibited glass transition temperatures between 275°C and 301°C, 10% weight loss temperatures ( Td10s) ranging from 502°C to 516°C, and char yields of 51–61% at 800°C under nitrogen atmosphere. Flexible and strong polymer films cast from DMAc solutions showed tensile strengths of 77.4–93.2 MPa, elongations at break of 9.2–14.3%, and initial moduli of 2.06–2.82 GPa. The polymer films also had good dielectric properties with dielectric constants of 3.22–3.50 (1 M Hz) and dissipation factors of 3.20–3.96 × 10−3, and acceptable electrical insulating properties, as well as low water uptake between 1.26% and 1.78%, and high transparency with an ultraviolet–visible absorption cutoff wavelength in the range of 330–371 nm. The remarkable combined features ensure these polymers to be ideal candidate materials for advanced microelectronic industry and other related applications.

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A series of fluorine‐containing branched sulfonated polyimide (Fb‐SPI) membranes with different degrees of branching (0–12 %) were synthesized through polycondensation. The chemical structure of Fb‐SPI‐10 membrane was confirmed using ATR‐FTIR and 1H NMR spectroscopy. The physico‐chemical properties of Fb‐SPI membranes were systematically investigated and compared to linear SPI (l‐SPI) and Nafion 117 membranes. The vanadium‐ion permeabilities of Fb‐SPI membranes (2.45–0.99×10−7 cm2 min−1) are much lower than that of Nafion 117 (17.1×10−7 cm2 min−1) membranes. Besides, the chemical stability of Fb‐SPI membranes is superior to that of l‐SPI membranes. During 500‐time continuous cyclic charge‐discharge measurements, the VRFB assembled with a Fb‐SPI‐10 membrane shows higher coulombic efficiency (98.4–99.7 %), higher or close energy efficiency (69.0–79.7 %) from 40 to 80 mA cm−2, and higher or close capacity retention (52.8–100 %) from 40 to 70 mA cm−2 compared with a device using a Nafion 117 membrane. All of these results demonstrate that the as‐selected Fb‐SPI‐10 membrane has promising potential for VRFB applications.

A new diamine bearing flexible ether, rigid pyridine, and bulky anthrone pendent group, 10,10-bis[4-(4-amino-2-pyridinoxy)phenyl]-9(10 H)-anthrone (BAPPA), was prepared in three steps from anthrone. BAPPA was reacted with six conventional aromatic dianhydrides in N, N-dimethylacetamide (DMAc) to form the corresponding new poly(ether imide)s (PEIs) via the poly(ether amic acid) (PEAA) precursors with inherent viscosities ranging from 0.85 dL g−1 to 1.26 dL g−1 and thermal imidization. All the PEAAs could be cast from DMAc solution and thermally converted into transparent, flexible, and tough PEI films with tensile strength of 72.2–112.4 MPa, tensile modulus of 1.8–2.1 GPa, and elongation at break of 10–18%. These PEIs were predominantly amorphous and displayed excellent thermal stability with the glass transition temperature of 290–388°C, the 5% weight loss temperature of 480–514°C, and the residue of 68–43% at 800°C in nitrogen. The PEIs derived from 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride and 4,4′-hexafluoroisopropylidenediphathalic anhydride exhibited excellent solubility in organic solvents such as N-methyl-2-pyrrolidinone, DMAc, N, N-dimethylformamide, pyridine, and even in tetrahydrofuran. Meanwhile, these PEIs also exhibited high optical transparency with the ultraviolet cutoff wavelength in the 374–427 nm range and the wavelength of 80% transparency in the range of 468–493 nm.

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