Derivatization of poly(benzimidazole) (PBI) with methyl groups generates poly(dimethyl benzimidazolium) (PDMI), an anion exchange material. By using a simple ion exchange process, it is possible to produce PDMI salts with a variety of counter-ions. Anionic conductivity (2.7 ± 0.33 to 8.5 ± 0.5 × 10−3 S cm−1) for the PDMI membranes was found to be surprisingly high even though the membranes generally exhibit very low water uptakes. To the best of our knowledge, this represents the first report on the anionic conductivity of poly(dialkyl benzimidazolium) salts, despite the large body of literature on PBI and on molecular imidazolium salts.
