A series of fluorinated sulfonated poly (ether amide)s (SPAs) were synthesized for proton exchange membrane fuel cell applications. A polycondensation reaction of 4,4'-oxydianiline, 2-sulfoterephthalic acid monosodium salt, and tetrafluorophenylene dicarboxylic acids (terephthalic and isophthalic) or fluoroaliphatic dicarboxylic acids produced SPAs with sulfonation degrees of 80-90%. Controlling the feed ratio of the sulfonated and unsulfonated dicarboxylic acid monomers afforded random SPAs with ion exchange capacities between 1.7 and 2.2 meq/g and good solubility in polar aprotic solvents. Their structures were characterized using NMR and FT IR spectroscopies. Tough, flexible, and transparent films were obtained with dimethylsulfoxide using a solution casting method. Most SPA membranes with 90% sulfonation degree showed high proton conductivity (>100 mS/cm) at 80 °C and 100% relative humidity. Among them, two outstanding ionomers (ODA-STA-TPA-90 and ODA-STA-IPA-90) showed proton conductivity comparable to that of Nafion 117 between 40 and 80 °C. The influence of chemical structure on the membrane properties was systematically investigated by comparing the fluorinated polymers to their hydrogenated counterparts. The results suggest that the incorporation of fluorinated moieties in the polymer backbone of the membrane reduces water absorption. High molecular weight and the resulting physical entanglement of the polymers chains played a more important role in improving stability in water, however. OPEN ACCESSPolymers 2011, 3 223
To investigate how quaternary ammonium ion structure affects the membrane stability and conductivity property of alkaline exchange membrane (AEM), we synthesized a series of polysulfones (PSUs) functionalized with various ammonium hydroxide groups. Ammonium ions with different steric environments were prepared by our recently developed Suzuki cross-coupling reactions of borylated polysulfone. We used two different synthetic strategies for the final polymers: In path A, like a general process for AEMs amine functional groups are first introduced to the PSU and quarternized afterward. In path B, pre-quarternized ammonium ions are directly introduced to the PSU.
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