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Summary: Poly(2,5‐benzimidazole) (ABPBI) was synthesized in a novel polymerization medium containing CH3SO3H and P2O5. 3,4‐Diaminobenzoic acid, a monomer for ABPBI, is soluble in the medium and the polymerization was therefore performed in a homogeneous state. It produced polymer fibers, thus simplifying the work‐up process. The membrane was cast directly from the polymerization mixture. Proton conductivities of the ABPBI membranes ranged from 0.02 to 0.06 S · cm−1 above 100 °C, without humidification, and the tensile strength of the membrane was approximately 100 MPa.Synthesis of ABPBI in a medium containing methanesulfonic acid and P2O5.imageSynthesis of ABPBI in a medium containing methanesulfonic acid and P2O5.

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Summary: Fuel cells were designed for high temperature operations. Poly[2,2′‐(m‐phenylene)‐5,5′‐bibenzimidazole] (PBI) was synthesized in a solution of P2O5, CH3SO3H, and CF3SO3H. The PBI was dissolved in a mixture of CF3CO2H and H3PO4 and the solution was used for the preparation of Pt catalyst slurry for membrane electrode assembly. The single cell showed a current density of 280 mA · cm−2 at a cell voltage of 0.5 V with feeds of H2 and O2 at 160 °C and without external humidification. magnified image

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