Low-cost polymers that possess high alkaline chemical stability could serve as anion exchange membranes and enable long-lasting alkaline fuel cell performance, where the alkaline fuel cell is a low-cost alternative to the well-adopted commercial proton exchange membrane fuel cell. In this study, five styrene-based poly(ionic liquids) (PILs) containing (covalently linked) saturated N-heterocyclic cations with various ring sizes (i.e., methylpyrrolidinium, methylpiperidinium, methylazepanium, methylazocanium, and methylazonanium) were synthesized and characterized. For PILs containing methylpyrrolidinium, methylpiperidinium, methylazepanium, methylazocanium, high alkaline chemical stability was observed after 4 weeks in 40 mol equiv of KOH (1.0 M in D2O) at 80 °C as evidenced by 1H NMR spectroscopy. Additionally, ion conductivity of all PILs increased by orders of magnitude with increasing water content, where a master percolation power law curve was observed, i.e., similar conductivity versus water volume fraction for all PILs regardless of cation size. These results provide insights on incorporating styrene-based PILs containing saturated N-heterocyclic cations as novel building blocks for anion exchange membranes.

Alkaline poly(ionic liquids) with methylpyrrolidinium, methylpiperidinium, methylazepanium, methylazocanium, and methylazonanium cations

2019 Fall National Meeting

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