Partially fluorinated and ammonium-functionalized terpolymers: Effect of aliphatic groups on the properties of anion conductive membranes

Synthesis and properties of a series of ammonium-containing terpolymers (QPAF-3) as anion conductive membranes are reported. The QPAF-3s composed of perfluoroalkylene, alkylene, and ammonium-functionalized phenylene groups without heteroatom linkages in the main chain were synthesized via nickel-mediated polycondensation reaction, followed by chloromethylation, quaternization, and ion exchange reactions. Self-standing, bendable membranes were obtained by solution casting. The QPAF-3 membrane with optimized terpolymer composition and ion exchange capacity (1.46 meq g⁻¹) showed high hydroxide ion conductivity (123 mS cm⁻¹ in water at 80 °C). The alkaline stability test in 1 M KOH for 1000 h at 80 °C and the post-test analysis with IR spectra and tensile strength suggested that ammonium groups were likely to be decomposed while the polymer main chain was chemically more robust. The presence of the alkylene groups in the terpolymers lowered solubility, glass transition temperature, and elongation property of the resulting membranes.