Novel Fluoropolymer For Fuel Cells

Scientists at Sumitomo Chemical are reporting a new type of sulfonated fluoropolymer that is a potential breakthrough in developing polymer-electrolyte membranes (PEMs) for fuel cells (Macromolecules, DOI: 10.1021/ma901953e). In PEM fuel cells, the polymer layer serves to separate the electrodes and reactants, but it must also permit hydrogen ions to migrate through with little resistance. Because of their high conductivity and chemical stability, perfluoroalkyl sulfonic acid polymers are the most commonly used membrane materials. However, these materials are expensive and don’t function well at higher temperatures, which limits fuel-cell efficiency. Chemists have therefore been seeking less expensive membrane materials with better heat resistance. One candidate is an aromatic polymer containing sulfonic acid groups. Sumitomo’s Ken Yoshimura and Katsuhiko Iwasaki combined the best structural features of the two polymer types via a copper-coupling reaction to create the novel polymer: a poly(phenylene ether sulfone) with pendant perfluoroalkyl sulfonic acid side chains. Initial tests indicate that the polymer has better fuel-cell performance, heat resistance, and mechanical properties than current commercial PEMs, the researchers note.