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Two synthesis routes for the preparation of novel base-modified polysulfones (PSUs; Udel) were investigated: (1) the addition of the basic aromatic ketones 2,2Ј-dipyridylketone and 4,4Ј-bis-(diethylamino)benzophenone and the basic aromatic aldehydes N,N-dimethylamino-benzaldehyde, pyridine-2-aldehyde, pyridine-3-aldehyde, and pyridine-4-aldehyde to lithiated PSU and (2) the reaction of lithiated PSU with basic aromatic carboxylic acid esters such as 4-N,N-dimethylaminobenzoic acid ethylester, pyridine-2-carboxylic acid ethylester, pyridine-3-carboxylic acid ethylester, and pyridine-4-carboxylic acid ethylester. Both synthesis routes lead to a high degree of conversion, without the occurrence of crosslinking. This is remarkable, especially for the reaction of lithiated PSU with the ester compounds, because the O(CAO)OAr groups formed by the reaction of the ester with PSU-Li are not further converted with the remaining PSU-Li sites to (crosslinked) PSUOC(OOLi)OArOPSU alcoholates, as normally observed when esters are reacted with Li-organic compounds. Starting with dilithiated PSU, we obtained degrees of substitution of 0.8 -2 groups per PSU repeating unit. The structures and compositions of the modified PSU polymers were confirmed with NMR spectroscopy and elemental analysis. The modified polymers were also characterized via thermogravimetric analysis (thermal stability). Interestingly, the product of the reaction of lithiated PSU with 4,4Ј-bis-(diethylamino)benzophenone could be oxidized to a deep blue polymeric dye that showed proton self-conductivity.

The preparation and characterization of different types of proton‐conducting polymer blend membranes are presented in this paper. The investigations are focused on the determination of the thermal stability of the membranes, because thermal stability is one of the important parameters for the application of the membranes in polymer electrolyte fuel cells. In addition to the thermal stability, chemical stability, proton conductivity and mechanical strength are required. The characterization of the membranes was performed by thermogravimetry (TGA), a combined TGA and FTIR analysis where infrared spectroscopy is used for the determination of decomposition products, and experiments on the dependence of water uptake (swelling) of the membranes on temperature. Ionically cross‐linked membranes have been investigated. The TGA‐FTIR coupling experiments showed clearly, that the decomposition of the membranes starts at ≈ 230 °C, and that in some cases the principal membrane component which is sulfonated polyaryletherketone splits off SO2 at slightly lower temperature in the membrane than in the pure substance. Most of the other polymeric components of the blend membranes were slightly more stable in the membrane than in the pure form. The ionically cross‐linked membranes were tested in direct methanol fuel cells as well as in a H2/air fuel cell and exhibit a performance which compares favorably with standard membranes.

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