Elastic Long-Chain Multication Cross-Linked Anion Exchange Membranes

Juanjuan Han, Liang Zhu, Jing Pan, Tawanda J. Zimudzi, Ying Wang, Yanqiu Peng, Michael A. Hickner, Lin Zhuang

Research output: Contribution to journalArticlepeer-review

104 Scopus citations

Abstract

Anion exchange membranes (AEMs) are a promising class of materials that enable non-noble metals to be used as catalysts in fuel cells. Compared to their acidic counterparts, typically Nafion and other perfluorosulfonate-based membranes, the low OH- conductivity in AEMs remains a concern as these materials are developed for practical applications. Cross-linked macromolecular structures are a popular way to optimize the trade-off between the ionic conductivity and the water swelling of AEMs with high ion exchange capacities (IECs). However, common cross-linked AEMs (e.g., x(QH)QPPO) that have high degrees of cross-linking with low molecular weight between cross-links are usually mechanically brittle. Moreover, the cross-links in AEMs can hinder the transport of OH-, leading to unsatisfactory conductivities. Here we report a series of elastic and highly conductive poly(2,6-dimethylphenylene oxide) (PPO)-based AEMs (x(QH)3QPPO) containing flexible, long-chain, multication cross-links. The strength and flexibility of the x(QH)3QPPO samples are significantly improved as compared to the conventional x(QH)QPPO membranes and multication un-cross-linked materials reported previously. The high conductivities in these new materials (x(QH)3QPPO-40, IEC = 3.59 mmol/g, σOH- = 110.2 mS/cm at 80 °C) are attributed to the distinct microphase separation observed in the x(QH)3QPPO membranes by SAXS and TEM analyses. Furthermore, the x(QH)3QPPO samples exhibit good dimensional (swelling ratio of x(QH)3QPPO-40 is 25.0% at 80 °C) and chemical (22% and 25% decrease in IEC and OH- conductivity in 1 M NaOH at 80 °C for 30 days, respectively) stabilities, making this cross-linking motif suitable for potential membrane applications in fuel cells and other electrochemical devices.

Original languageEnglish (US)
Pages (from-to)3323-3332
Number of pages10
JournalMacromolecules
Volume50
Issue number8
DOIs
StatePublished - Apr 25 2017

All Science Journal Classification (ASJC) codes

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry

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