(267a) Composite Proton Exchange Membranes From Zirconium-Based Solid Acids and PVDF/Acrylic Polyelectrolyte Blends

Organic/inorganic composite ( hybrid) proton exchange membranes (PEMs) are of interest due to potential benefits in conductivity, mechanical, and transport properties that may arise by the incorporation of inorganic nanofillers into the polymeric matrix. Our previous work showed that entirely polymeric membranes based on blends of poly(vinylidene fluoride) (PVDF) and covalently-crosslinked sulfonated acrylic polyelectrolytes (PE) compare favorably against perfluorosulfonic acid-based counterparts (e.g., Nafion®) in terms of proton conductivity and mechanical properties. In this study we explore the ability to enhance these properties by the insertion of various zirconium-based nanoparticles into the PVDF/PE matrix, giving place to tri-phase organic/organic/inorganic composite membranes. Dispersion of nanoparticles in the polymer matrix was limited by unfavorable particle-polymer interactions resulting in severe aggregation at high particle loadings (5 wt%). Nevertheless, a general improvement in proton conductivity was evidenced in composite membranes with low to medium nanoparticle loadings (0.5 to 1 wt%). This beneficial effect was particularly noticeable in membranes manufactured from highly crystalline PVDF homopolymers (7% to 14.3% increment), where the nanoparticles induced a ?healing? effect by providing proton-conducting paths between non-crosslinked PE channels separated by dense PVDF areas arising from large PVDF crystallites. Similarly, tensile properties were enhanced at identical particle loadings (19.5% to 22.5% elastic modulus increment); especially in membranes containing more flexible PVDF:HFP copolymers, where a reinforcing stiffening effect was evident. While addressing nanoparticle dispersion is imperative, the results presented herein indicate promise inherent to the development of zirconium-nanocomposite PEMs.