(121d) Proton Conducting Sulfonated Poly(ionic liquid) Block Copolymers

Poly(ionic liquid) (PIL) block copolymers (where one block contains ionic liquid (IL) chemistry) have been investigated as lithium ion conducting solid polymer electrolytes for batteries and hydroxide conducting membranes and ionomers for alkaline fuel cells,¹ while sulfonated block copolymers (where one block contains sulfonic acid) have been intensively explored as proton conducting membranes and ionomers for proton exchange membrane fuel cells.² Conjoining these two materials into one, i.e., sulfonated PIL block copolymers, where one block contains IL chemistry and the other contains sulfonic acid, is of significant interest where more than one single-ion conductor is necessary, specifically when ion transport can be segregated into separate nanostructured continuous domains. Recently, the synthesis of a lithium ion conducting sulfonated PIL diblock copolymer was reported,³ where the styrene-based sulfonic acid block contained mobile lithium (Li⁺) cations and the acrylate-based PIL block contained mobile bis(trifluoromethylsulfonyl)imide (TFSI^-) anions. In this work, a proton conducting sulfonated PIL diblock copolymer, consisting of a styrene-based sulfonic acid block containing mobile protons (H⁺) and a styrene-based PIL block containing mobileTFSI^- anions, was successfully synthesizedviareversible addition-fragmentation chain transfer (RAFT) polymerization, followed by post-functionalization, anion exchange metathesis, and sulfonation. The synthesis, chemical, thermal, and physical properties, and ion conductivity of this new block copolymer will be presented. This work provides a new materials platform, where more than one single-ion conductor is of interest for various electrochemical applications.

1. Meek, K. M.; Elabd, Y. A., Polymerized ionic liquid block copolymers for electrochemical energy. J Mater Chem A 2015, 3(48), 24187-24194.
2. Elabd, Y. A.; Hickner, M. A., Block Copolymers for Fuel Cells. Macromolecules 2011,44(1), 1-11.
3. Meek, K. M.; Elabd, Y. A., Sulfonated Polymerized Ionic Liquid Block Copolymers. Macromolecular Rapid Communications 2016, 37(14), 1200-1206.