Partially Fluorinated Multiblock Poly(arylene ether sulfone) Membranes for Fuel Cell Applications

Sulfonated poly(arylene ether sulfone) (SPAES-F series) membranes, which are partially fluorinated multiblock polymers containing Bisphenol 6F (6F-BPA), are synthesized. The membranes exhibit less water uptake and higher ion conductivity at similar ion exchange capacity (IEC) values compared to previous SPAES membranes containing identical hydrophilic blocks. This is attributed to the presence of 6F-BPA in the hydrophobic block, which enhances hydrophobicity and promotes phase separation, as observed through transmission electron microscopy analysis. F4 (IEC = 2.4 meq g⁻¹) shows superior ion conductivity than Nafion NRE212 membrane irrespective of the humidity level. Furthermore, the SPAES electrolyte membrane of 1.5 meq g⁻¹ produces better performance than NRE212, yielding a current density of 488 mA cm⁻² at 80 °C, 80% RH, and 0.6 V. In 50% RH at 80 °C, SPAES with 1.5 meq g⁻¹ exhibits a cell resistance and fuel cell performance comparable to those of NRE212; clearly, regulating hydrophobicity and hydrophilicity is crucial for enhanced performance.