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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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Low-cost polymers poly(styrene) and poly(a-methylstyrene) have been sulfonated followed by blending with PBIOOV R (30 wt % sulfonated ionomer, 70 wt % PBIOO). At this polymer ratio the sulfonated ionomer served as the macromolecular acidic crosslinker which led to enhancement of the PBIOO stability. Both membrane types were treated with Fenton's Reagent to investigate their resistance to oxidation and radical attack. Indeed, the blend membranes showed enhanced stability in oxidative conditions compared to the pure PBIOO membranes. Furthermore, the sulfonated poly(a-methylstyrene)-PBIOO blend membrane showed less weight loss during and after Fenton's Test than the corresponding poly(styrene sulfonic acid)-PBIOO membrane. Assuming all the characteristics of the blend membrane before and after the Fenton's Test, we concluded for a partial degradation of both sulfonated poly(styrene)s, whereas they remain in the blend membrane matrix due to the acid-base crosslinking. Thus, since the sulfonated poly((a-methyl)styrene)-PBIOO blend membranes conserved their integrity even after Fenton's Test they can be regarded as potential low-cost high-T fuel cell membranes.

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.

The low-cost polymers poly(styrene) and poly(α-methylstyrene) have been sulfonated in a first step. Then both sulfonated ionomers have been blended with PBIOO® (30 wt% sulfonated ionomer, 70 wt% PBIOO), the sulfonated ionomer serving as acidic cross-linker which enhances the PBIOO stability. Both membrane types were treated with Fentons Reagent to investigate their oxidative stability. Of particular interest was whether the poly(α-methylstyrene) ionomer was more stable against radical attack. It was indeed found that the PBIOO-sulfonated poly(α-methylstyrene) blend membrane showed less weight loss during and after Fenton Test than the respective poly(styrene sulfonic acid) PBIOO-containing membrane. The macromolecules are partially degrading by radical attack to the main chain of the sulfonated poly(α-methylstyrene) polymers but still remain in the blend membrane matrix due to acid-base interactions. Since the PBIOO/sulfonated poly(α-methylstyrene) blend membranes conserved their integrity even after Fentons Test they can be regarded as interesting low-cost high-T fuel cell membranes.

A novel partially fluorinated and sulfonated poly(arylene sulfone) was successfully synthesized via nucleophilic polycondensation of 2,2-Bis(4-fluorophenyl)hexafluoropropane with 4,4'-Thiobisbenzenethiol (TBBT). In a second step the prepared poly(arylene sulfide) was oxidized to poly(arylene sulfone). 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 groups in the last years. All membranes were analyzed in terms of water uptake, thermal and oxidative stability. Additional the blend membranes were characterized by gel permeation chromatography (GPC). The novel poly(arylene)sulfone SPSO blend shows a high molecular weight and an excellent TSO3H, onset of 334°C. The proton conductivity is 0,11 S/cm and the water uptake reaches 30%.

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