(277f) Sulfonated Poly(Arylene Ether Sulfone)-Inorganic Oxide Nanocomposite Membranes Containing Organic-Metallic Complexes

Proton conductive composites have been highlighted as one of potential proton exchange membranes (PEMs) owing to their unique properties such as high processability and excellent mechanical properties derived from organic polymers and inorganic particles, respectively. The composite type PEMs are expected to substitute or modify commercial perfluorinated sulfonic acid (PFSA) membranes including Nafion^®. There have been trials to incorporate inorganic oxides for self-humidification and suppression of methanol crossover. Inorganic oxide particles are typically added into the polymer matrix via sol-gel synthetic route using alkoxide precursor. In spite of homogeneous dispersion, sol-gel process was affected by numerous factors including kinds of alkoxide precursors, pH in the reaction medium, solvents, reaction temperature and pressure. These factors lead to different morphologies and physico-chemical properties in the resulting hybrid membranes. In the present study, nanosized inorganic fillers were incorporated in the form of organometallic complexes which were composed of organic dispersants and functional inorganic fillers. Their synergetic effect led to overall improvement of membrane performances such as proton conductivity, dimensional stability, and resistance to hydrolytic and free radical attack. Nanophase-separated inorganic oxide along with organic dispersants also hindered methanol transport across sulfonated poly(arylene ether sulfone) (SPAES)-inorganic oxide nanocomposite membranes, and contributed to excellent electrochemical single cell performance (130 mA/cm² at 0.4 V, and maximum 160 mW/cm² at 0.29 V) as compared with Nafion 117 (105 mA/cm² at 0.4 V, and maximum 120 mW/cm² at 0.34 V) under the same operation condition (90 ^oC and 1 M MeOH/ O₂).