Synthesis and Characterization of Perfluoro Quaternary Ammonium Ion Exchange Membranes for Fuel Cell Applications

摘要

In this work alkaline exchange membranes were prepared from the 3M perfluorinated ionomer by functionalization with two amine species that were further alkylated to quaternary ammonium cations. The methyl amine polymer was successfully quaternized to produce an ion exchange capacity (IEC) of 0.72 meq g~(-1), while the isopropyl amine did not quaternize resulting a negligible IEC of 0.02 meq g~(-1). Membrane swelling under a range of humidity conditions was characterized before and after thermal annealing through small angle x-ray scattering. Swelling in the methyl cationic membrane was isolated to the ionic domain and showed little change by thermal annealing. The as-cast aminated isopropyl membranes exhibited inconsistent morphological ordering and hysteresis during humidity cycling. Thermal annealing of the isopropyl amine membrane induced structural reorganization that resisted change during humidity cycling. This work highlights the importance of morphology and thermal conditioning of ion exchange membranes to produce consistent long-term performance.