(373f) Sulfonated Poly(Ionic Liquid) Block Copolymers As Ionomers in Ultra-Low Platinum Fuel Cells

Novel polymers that possess multiple desired properties (e.g., low-cost, high proton conductivity, high electrochemical stability, high ionic liquid (IL)-philicity, low degree of swelling) are of significant interest to enhance the oxygen reduction reaction kinetics (i.e., reduce required platinum catalyst) and therefore serve as a promising alternative to the widely used perfluorosulfonic acid ionomers (i.e. Nafion) in hydrogen fuel cells. In this study, a series of proton-conducting sulfonated poly(ionic liquid) block copolymers (S-PILBCPs), where one block contains sulfonic acid (sulfonated styrene: SS) and the other contains an IL moiety (vinylbenzylmethylimidazolium bis(trifluoromethylsulfonyl)imide: VBMIm-TFSI), was successfully synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization, followed by post-functionalization, anion exchange metathesis, and sulfonation. The resulting block polymers contain both mobile cations (H⁺) and mobile anions (TFSI^-) and exhibit high conductivity comparable to Nafion. Properties (chemical, thermal, morphology, ion conductivity) of the S-PILBCPs were explored as a function of block composition. Additionally, ion and water transport in the S-PILBCPs was explored as a function of IL additive composition. These results will be presented in relation to the efficacy of S-PILBCPs as ionomers in low-cost fuel cells.