Stable anion exchange membranes derived from fluorinated poly(aryl ethers) with quaternized fluorene units for fuel cell applications

A series of fluorinated poly(aryl ethers) containing benzyltrimethyl quaternary ammonium functionalized fluorene units (QPFAE) are synthesized via condensation polymerization, chloromethylation, and quaternization. Ionomer structure and the ion exchange capacity are confirmed by H-1-nuclear magnetic resonance spectroscopy. Other characterization techniques such as Fourier transform infrared spectroscopy, atomic force microscopy, thermogravimetric analysis, gel permeation chromatography, electrochemical impedance spectroscopy, Fenton, water-swelling, and hydrolytic aging tests are used to evaluate the physicochemical properties of the as-prepared QPFAE membranes. For the QPFAE membranes with ion exchange capacity of 0.95-1.94 mmol/g, they displayed low water uptake and methanol permeability (4.59-26.1 x 10(-8) cm(2)/s at 25 degrees C), fairly good dimensional stability, high mechanical toughness, as well as fine thermal-oxidative-hydrolytic stability and ion conductivity at least 10 mS/cm. The membranes also showed clear hydrophilic/hydrophobic phase-separation morphology. Furthermore, the QPFAE membranes could endure harsh basic conditions (1-4 mol/L NaOH solution) at 60 and 80 degrees C at least 240 h, keeping rather high mechanical toughness and ion conduction capability during the aging test. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46301.