For enhancing hydroxide ion conductivity, alkaline stability, and fuel cell performance of quaternaized aromatic/perfluoroaklyl copolymer (QPAF) membranes, ammonium groups attached to the polymer backbone have been investigated. The ammonium groups included dimethyl­butylamine (DMBA), dimethyl­hexylamine (DMHA), and 1,2-dimethyl­imidazole (DMIm) groups in comparison to the trimethyl­ammonium (TMA) group. DMBA turned to be the optimum ammonium group for QPAF membranes in terms of its high hydroxide ion conductivity based on well-connected and larger phase-separated morphology than that of QPAF-TMA with similar ion exchange capacity (IEC) value. QPAF-DMBA (IEC = 1.33 mequiv g–1) exhibited the highest hydroxide ion conductivity among the tested membranes up to 152 mS cm–1 in water at 80 °C, which was 1.6 times higher than that of QPAF-TMA (95 mS cm–1). In addition, QPAF-DMBA exhibited reasonable alkaline stability in 1 M KOH at 60 °C for 1000 h. The remaining conductivity was 44 mS cm–1 (58%) for QPAF-DMBA, while that for QPAF-TMA was 1.0 mS cm–1 (1%). QPAF-DMBA (IEC = 1.09 mequiv g–1) exhibited excellent stability in 1 M KOH at 80 °C without change in the ion conductivity (22 mS cm–1) for 500 h. The post-test membranes exhibited a minor degradation in QPAF-DMBA as suggested by FT-IR spectra and DMA analyses. An H2/O2 fuel cell was operated with the QPAF-DMBA membrane to achieve the maximum power density of 167 mW cm–2 at the current density of 0.42 A cm–2, which was higher than that (138 mW cm–2) for QPAF-TMA membrane under the same operating conditions.

Partially fluorinated aromatic polymer-based anion exchange membranes with propylene side chains exhibit high chemical stability and alkaline fuel cell performance.

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