Title of Paper:Ether spaced N-spirocyclic quaternary ammonium functionalized crosslinked polysulfone for high alkaline stable anion exchange membranes

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Date of Publication:2020-03-15

Journal:JOURNAL OF MEMBRANE SCIENCE

Included Journals:EI、SCIE

Volume:598

ISSN No.:0376-7388

Key Words:Anion exchange membrane; N-spirocyclic quaternary ammonium cation; Crosslinking; Ether spacer; Fuel cell

Abstract:N-spirocyclic cations containing anion exchange membranes (AEMs) possess excellent alkaline stability, but poor mechanical and conductive properties due to the rigid N-spirocyclic structure and lack of flexible side chain structural design. In this work, a flexible ether spaced N-spirocyclic quaternary ammonium functionalized side chain is proposed, in which hydroxyl substituted N-spirocyclic cation provides active grafting site with chloromethylated polysulfone through Williamson etherification. The flexible ether-oxygen spacer promotes aggregation of the rigid spirocyclic cations and thus significantly improves conductivity. The uniformly in-situ thermal crosslinking between benzene rings and the residue chloromethyl groups in polysulfone greatly enhances mechanical properties of the membranes. Constrained ring conformation of N-spirocyclic cation, ether spaced benzyl-free side chain, as well as the OH- blocking crosslinked networks endow an excellent alkaline stability to the membranes. The ether spaced N-spirocyclic containing membranes exhibit well micro-phase separation structure, up to around 85.7 mS cm(-1) of hydroxide conductivity at 80 degrees C, around 10.5 MPa of tensile strength in hydrated state and around 95.6% conductivity retention after immersion in 1 M KOH at 80 degrees C for 720 h. The performance is among the best N-spirocyclic functionalized AEMs reported in the literature.