POLYMER ELECTROLYTE MEMBRANE CONTAINING FLEXIBLE OLIGOMERIC PHENYLENE ETHER SEGMENTS WITH IMPROVED MEA PROCESSABILITY

摘要

Sulfonic acid-containing Poly(arylene ether)s are considered as essentially good structure for a polymer Electrolyte Membrane for especially direct methanol fuel cell (DMFC) because they are stable against hydrolysis and show relatively low methanol permeability. As methanol crossover from anode to cathode induces decrease in fuel efficiency and reduction of cell voltage, these polymers show high advantage against perfluorosulfonic acid membranes. Although their performance of polymer electrolyte membrane is highly expected in this point of view, drawback in the processability to prepare membrane-electrode assembly (MEA) exists. As MEA is usually prepared by hot-pressing of membrane with electrode containing PFSA ionomer as a binder, high glass transition temperatures of aromatic condensation polymers sometimes result in poor adhesion between them. The poor adhesion does not only induce difficulty to prepare good MEA, but also increase in MEA resistance and delamination of electrode from membrane during long term DMFC operation. To overcome this issue, synthesis of sulfonated polymers with lower glass transition temperature is a promising strategy, and ω,ω’-dihydroxy poly(1,4-phenylene ether)s (DHPE) were evaluated as a flexible monomer in the nucleophilic polymerization to form a low Tg polymer electrolyte membrane for DMFC.