A partially fluorinated and sulfonated poly(arylene sulfone) (SPSO) was successfully synthesized via nucleophilic polycondensation of 2,2‐bis(4‐fluorophenyl)hexafluoro‐propane with 4,4′‐thiobisbenzenethiol (TBBT). In a second step, the prepared poly(arylene sulfide) was oxidized to SPSO. The polymer was blended with the polybenzimidazole PBIOO® to obtain a mechanically stable membrane. This film was compared with other polymer blends, which were synthesized in our group in the last years. We were especially interested in the influence of different bridging groups such as ether, ketone, and sulfone groups. The affect on properties such as water uptake (WU), thermal stability, proton conductivity, and oxidative stability were analyzed in this work. Additionally, the blend membranes were characterized by gel permeation chromatography. The novel SPSO blend shows a high molecular weight, and its blend membrane with PBIOO has an excellent onset of SO3H group splitting‐off temperature (T SO 3H,onset) of 334 °C. The proton conductivity amounts to 0.11 S cm−1, and the water uptake reaches 30%. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

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Multiblock‐co‐polymers with different ion exchange capacities were synthesised by nucleophilic aromatic step‐growth polycondensation of hydrophilic and hydrophobic oligomers. The main focus of this work was to investigate the dependence of oligomer reactivity on molecular weight and how the reaction conditions need to be changed to obtain high‐molecular multiblock‐co‐polymers, consisting of long block segments. Multiblock‐co‐polymers composed of short oligomers could be synthesised under mild reaction conditions. The coupling of longer oligomers required more basic reaction conditions, because the reactive functional end‐groups were shielded by the long oligomeric main chain. The membranes were investigated further in terms of their properties relevant for use as polymer electrolyte membrane in direct methanol fuel cells (DMFCs). The mechanical stability of the acidic polymers was improved through ionical crosslinking with basic polybenzimidazole. A series of membranes was tested in a self‐ and in an air‐breathing DMFC.

This contribution comprises an overview in the development of ionomers/ionomer (blend) membranes for fuel cells. The topics include the development of novel sulfonated monomers and homoand copolymers; the preparation of ionically cross-linked membranes prepared by mixing these polymers with different polybenzimidazoles (PBI); the application of these membranes to PEFC and DMFC; development of novel base-excess PBI/sulfonated polymer/H 3 PO 4 blend membranes, and test of these membranes in fuel cells at intermediate fuel cell operation temperatures (170-200°C). These membranes have been tested in a DMFC. The i/U polarization curves of the membranes showed a better performance than Nafion ® . Acid-base blend membranes were also applied to the HyS electrolysis process, showing good stability and electrolysis performance. Phosphonated polymers and ternary blend membranes for the application in intermediate T fuel cells have been developed as well. These membranes showed good chemical stability rivalling that of pure PBI membranes.