Novel polyaromatic ionomers with large hydrophilic domain and long hydrophobic chain targeting at highly proton conductive and stable membranes

Abstract

A novel dihydroxyl monomer bearing 18 electron rich phenyl rings were synthesized and polymerized with other monomers bearing electron deficient phenyl rings to give dense and selective sites in macromolecules for post-sulfonation, which was successfully conducted in ClSO₃H/CH₂Cl₂ solution at room temperature in a subsequential step. The chemical structures were confirmed by ¹H NMR and FT-IR spectra. The ionic exchange capacity (IEC) was controlled to be from 0.65 to 1.21 mequiv g⁻¹ to afford considerable proton conductivity. Distinct phase separation was observed in the resulting membranes from SAXS profiles. The SPAEK-5 with an IEC of 1.21 mequiv g⁻¹ gave better proton conductivity than Nafion 117 at all tested temperatures under 100% relative humidity. The membranes exhibited an exceeding stability when immersing in Fenton's reagent (3 wt.% H₂O₂ + 2 ppm FeSO₄) at 80 °C. These properties make them promising candidates for electrochemical applications.