Synthesis and characterization of polysulfone-containing sulfonated side chains for direct methanol fuel cells

Two series of novel polysulfone-based ionomers containing pendant sulfonic acid groups (designated as PSf-sph-y and PSf-sna-z) have been prepared using commercially available polysulfone and sulfoaryl monomers. The synthesized ionomers have been characterized by nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. The thermal characterization data show that these polymers are stable up to 210 °C in acid form and 270 °C in salt form in air. Ion exchange capacity, water uptake, swelling, proton conductivity, and methanol permeability of the membranes have been investigated and compared with those of Nafion 115. The PSf-sna-z membranes bearing highly ionic groups on the flexible side chains show lower water uptake, swelling, and methanol permeability compared to the PSf-sph-y and Nafion 115 membranes. The optimized PSf-sna-58 membrane shows better performance in direct methanol fuel cells (DMFC) than Nafion 115 membranes.

► Polyelectrolytes bearing sulfonated side chains have been synthesized by a facile route and characterized.
► The membranes containing highly ionic groups on the flexible side chains exhibit low water uptake and swelling.
► The optimized membranes show better performances in DMFC than Nafion 115 membrane.