Cardo poly(arylene ether sulfone) block copolymers with pendant imidazolium side chains as novel anion exchange membranes for direct methanol alkaline fuel cell

A series of phenolphthalein-based cardo poly(arylene ether sulfone) (PES) block copolymers containing pendant imidazolium group (PI-PESs) were synthesized as novel anion exchange membranes for direct methanol alkaline fuel cells. These PI-PESs combine the advantages of pendant anion conductors on the polymer side chains with the thermochemical stabilities of the imidazolium group, showing high hydroxide conductivity, together with good physical and chemical stability under basic conditions. The hydroxide conductivity over 0.03 S/cm at 20 °C and 0.1 S/cm at 80 °C was obtained for the PI-PES membranes. In addition, PI-PES membranes show low permeability to methanol (below 6.74 × 10−8 cm2/s) and very high selectivity (over 3.7 × 105 S·s/cm3). These properties make the PI-PESs promising candidate materials for anion exchange membranes for direct methanol alkaline fuel cells.