Synthesis and characterization of perfluoro quaternary ammonium anion exchange membranes

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2013-12, Vol.51 (24), p.1761-1769
• Main Authors: Vandiver, Melissa A., Horan, James L., Yang, Yuan, Tansey, Emily T., Seifert, Söenke, Liberatore, Matthew W., Herring, Andrew M.
• Format: Article
• Language: English
• Subjects: Anion exchanging; Applied sciences; Chemical modifications; Chemical reactions and properties; Exact sciences and technology; Exchange resins and membranes; fluoropolymers; Forms of application and semi-finished materials; ionomers; Membranes; NMR; Organic polymers; Physicochemistry of polymers; Polymer industry, paints, wood; SAXS; Technology of polymers
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.23171

In this study, new alkaline exchange membranes were prepared from the perfluorinated 3M ionomer with various quaternary ammonium cations attached with sulfonamide linkage. The degree of functionalization varied depending on the cation species, resulting in different ion exchange capacities (IECs), 0.33–0.72 meq g−1. There was evidence of polymer degradation when the films were exposed to hydroxide, and hence all membrane characterization was performed in the chloride form. Conductivity was dependent on cation species and IEC, Ea = 36–59 kJ mol−1. Diffusion of water through the membrane was relatively high 1.6 × 10−5 cm2 s−1 and indicated restriction over a range of diffusion times, 6–700 ms. Water uptake (WU) in the membranes was generally low and the hydration level varied based on cation species, λ = 6–11. Small‐angle scattering experiments suggested ionic aggregation, 37–42 Å, independent of cation species but slight differences in long‐range order with cation species. © 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1761–1769, 2013 Anion exchange membranes (AEMs) must have high hydroxide conductivity and be chemically stable for the lifetime of the fuel cell. Proton exchange membrane fuel cells have demonstrated that hydration and polymer morphology can significantly affect ion conduction in the membrane. Understanding the role of water and morphology on ionic transport in AEMs is important to direct the development of high performing membranes.