Sulfonated polyaryletherketone with pendant benzimidazole groups for proton exchange membranes

We synthesized a range of sulfonated polyaryletherketone (x%SCBI-SPAEK-6F) with pendant benzimidazole side groups at a tunable molar percentage (x within 5–15%) for potential application as proton exchange membrane (PEM). A systematic study had been undertaken to study the performance and the underlying structure-properties relationship of PEMs fabricated by those novel amphoteric polymers. It was found that the dimensional stability, oxidative stability and methanol resistance performance of x%SCBI-SPAEK-6F membranes were significantly improved with the increase of the benzimidazole content due to the acid-base interaction. In particular, the 5%SCBI-SPAEK-6F membrane exhibited a relative selectivity (10.5 × 103 S s cm−3) almost 20 times higher than that of Nafion117 membrane at 75 °C, demonstrating the significant promoted proton conductivity (0.35 S cm−1) and reduced methanol penetration (6 × 10−7 cm2 s−1) by the ionic barrier. With such superior performance, these polymers are promising for the fabrication of practical proton exchange membranes in commercial fuel cells.