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Polybenzimidazole membranes imbibed with acid are emerging as a suitable electrolyte material for high‐temperature polymer electrolyte fuel cells. The oxidative stability of polybenzimidazole has been identified as an important issue for the long‐term durability of such cells. In this paper the oxidative degradation of the polymer membrane was studied under the Fenton test conditions by the weight loss, intrinsic viscosity, size exclusion chromatography, scanning electron microscopy and Fourier transform infrared spectroscopy. During the Fenton test, significant weight losses depending on the initial molecular weight of the polymer were observed. At the same time, viscosity and SEC measurements revealed a steady decrease in molecular weight. The degradation of acid doped PBI membranes under Fenton test conditions is proposed to start by the attack of hydroxyl radicals at the carbon atom linking imidazole ring and benzenoid ring, which may eventually lead to the imidazole ring opening and formation of small molecules and terminal groups for further oxidation by an endpoint oxidation.

A partially fluorinated polyether ionomer from polycondensation of decafluorobiphenyl with 2,2‐bis(4‐hydroxyphenyl)hexafluoropropane, followed by sulphonation with H2SO4 (60% SO3), has been prepared and optimised in terms of molecular weight and sulphonation degree. The partially fluorinated ionomer has been blended with poly(2,2′‐m‐phenylene‐5,5′‐bibenzimidazole) (PBI), yielding base–acid blends with PBI in excess. The base–acid blend membranes have been characterised in terms of solubility in DMAc, water uptake and oxidative stability by immersion in aqueous 5 wt.‐% H2O2 solutions and Fenton's Reagent, respectively.

Due to an unfortunate mistake, the publishers regret that Fig. 7 on p.196 of the above article was incorrect. The correct figure is shown below. The editorial team apologizes for any inconvenience this may have caused. 0 0,2 0,4 0,6 0 50 100 150 200 Temperature / ° C Conductivity / Scm-1 100%H3PO4 PPA-membrane, ADL=32, RH=0% Nafion 117, RH=95% DMAc-membrane, ADL=5.7 TFA-membrane, ADL=6, RH=5% PBI-1b, ADL=11, RH=10% Fig.7 Proton conductivity of acid doped PBI and PBI-1b blend membranes as a function of temperature. As a comparison, data for 100% phosphoric acid and Nafion 117 are also included. The PPA-cast membrane was with an acid doping level of 32 and at relative humidity of 0% [20]; The DMAc-cast membrane was with an acid doping level of 5.7 and under atmosphere with a water-to-air ratio of about 0.7 [6]; The TFA membrane was with an acid doping level of 6.0 and at relative humidity of 5% [7].

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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