Preparation and properties of sulfonated poly(phenylene arylene)/sulfonated polyimide (SPA/SPI) blend membranes for polymer electrolyte membrane fuel cell applications

A novel series of sulfonated poly(phenylene arylene)s (SPAs) were successfully synthesized from 2,5-dichloro-3′-sulfobenzophenone (DCSB) and 2,2′-bis[4-(4-chlorobenzoyl)]phenoxyl perfluoropropane (BCPPF) by Ni(0)-catalyzed coupling polymerization, and subsequently used as the start materials to prepare blend membranes with sulfonated polyimide (SPI) for polymer electrolyte membrane fuel cell (PEMFC) applications. The miscible structure of the prepared blend membranes was confirmed by scanning electron microscopy (SEM). The properties required for a PEM such as ion exchange capacity, water uptake, solution uptake and dimensional change and/or in water or methanol solutions, proton conductivity and hydrolytic stability were investigated in details. The obtained blend SPA/SPI membranes showed rather high proton conductivities in both the plane and the thickness direction of the membrane. They exhibited slightly anisotropic proton conductivity in water with σ⊥/∥ values in the range of 0.85–0.90, irrespective of the introduction of SPI (σ⊥/∥ = 0.73). They also showed significantly enhanced stability in water and methanol solutions compared with the corresponding SPA membranes. All the results indicated that this type of blend membranes were quite promising candidates for PEMFC applications