Ion transport properties of mechanically stable symmetric ABCBA pentablock copolymers with quaternary ammonium functionalized midblock

Sedef P Ertem, Benjamin R. Caire, Tsung Han Tsai, Di Zeng, Melissa A. Vandiver, Ahmet Kusoglu, Soenke Seifert, Ryan C. Hayward, Adam Z. Weber, Andrew M. Herring, E. Bryan Coughlin, Matthew W. Liberatore

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Anion exchange membranes (AEMs) are a promising class of materials for applications that require selective ion transport, such as fuel cells, water purification, and electrolysis devices. Studies of structure–morphology–property relationships of ion-exchange membranes revealed that block copolymers exhibit improved ion conductivity and mechanical properties due to their microphase-separated morphologies with well-defined ionic domains. While most studies focused on symmetric diblock or triblock copolymers, here, the first example of a midblock quaternized pentablock AEM is presented. A symmetric ABCBA pentablock copolymer was functionalized to obtain a midblock brominated polymer. Solution cast films were then quaternized to obtain AEMs with resulting ion exchange capacities (IEC) ranging from 0.4 to 0.9 mmol/g. Despite the relatively low IEC, the polymers were highly conductive (up to 60 mS/cm Br at 90 °C and 95%RH) with low water absorption (<25 wt %) and maintained adequate mechanical properties in both dry and hydrated conditions. X-ray scattering and transmission electron microscopy (TEM) revealed formation of cylindrical non-ionic domains in a connected ionic phase.

Original languageEnglish (US)
Pages (from-to)612-622
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume55
Issue number7
DOIs
StatePublished - Apr 1 2017
Externally publishedYes

Keywords

  • anion exchange membrane
  • block copolymers
  • conducting polymers
  • inverse morphology
  • ion conductivity
  • ionomers
  • mechanical properties
  • mechanically robust
  • morphology
  • pentablock copolymer

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