A Soluble and Conductive Polyfluorene Ionomer with Pendant Imidazolium Groups for Alkaline Fuel Cell Applications

Solvent processable polyfluorene ionomers with pendant imidazolium groups were synthesized and characterized. The synthesized polymeric membranes are transparent, flexible, and mechanically strong and exhibit hydroxide ion conductivity above 10(-2) S/cm at room temperature. The membranes are soluble in polar aprotic solvents such as DMSO and DMF, while insoluble in water and aqueous methanol. The solubility properties of polyfluorene ionomers enable the use for not only alkaline anion-exchange membrane but also ionomer electrode material. H-1 NMR and hydroxide ion conductivity measurements demonstrated an excellent chemical stability of the synthesized polyfluorene ionomers in high-pH solution at elevated temperatures. The results of the study suggest a feasible approach for the synthesis and practical applications of alkaline anion-exchange membranes (AEMs).