The sulfonation selectivity of seven poly(ether ether ketone)s (PEEKs) was investigated, and several possessed targeted single-or double-substituted sites per repeated unit on pendant phenyl groups via the postsulfonation approach. The presence of the various pendant groups enabled postsulfonation to occur under mild reaction conditions, in much shorter times than required for the sulfonation of commercial PEEK. A series of poly(ether ketone)s (PEKs) with ion exchange capacity of 2.23-0.84 mequiv/g could be realized by controlling the length of unsulfonated segments of both homopolymers and copolymers. These side-group sulfonation polymers had excellent mechanical properties, good thermal and oxidative stability, and good dimensional stability in hot water. The methanol permeability values of Me-SPEEKK, Me-SPEEKDK, Ph-SPEEKK, and Ph-SPEEKDK at room temperature were in the range 3.31 × 10 -7 -9.55 × 10 -8 cm 2 /s, which is several times lower than that of Nafion 117. Me-SPEEKK and Ph-SPEEKK also exhibited high proton conductivity of 0.15 S/cm at 100°C, which is higher than that of Nafion 117. Transmission electron microscopy analysis was used to observe their microstructure for evidence of microphase separation of ionic and hydrophobic domains. The results showed these side-group-acid materials are possible inexpensive candidate materials for proton exchange membranes in fuel cell applications.

The study represents a comparative investigation of three series of high molecular weight aromatic poly(aryl ether ether nitrile) copolymers (SPAEEN-n), containing different sulfonated naphthalene groups, where n (in the range 0-80 mol %) refers to molar percentage of repeat units containing the sulfonic acid function. The three series of SPAEEN-n copolymers were synthesized via potassium carbonate-mediated nucleophilic polycondensation reactions of commercially available monomers: 2,6-difluorobenzonitrile (2,6-BFBN), one of three dihydroxynaphthalenesulfonate (DHNS) monomers, and unsulfonated 4,4′-biphenol (BP), incorporated for the purpose of adjusting the sulfonic acid content. The incorporation of the sulfonated repeat unit into copolymers and their structures were confirmed by 1 H NMR and FT-IR spectroscopy. Products were solvent-cast into membranes of varying ionic content as proton exchange membrane (PEM) materials for fuel cells applications. Ion exchange capacity (IEC), thermal stabilities, swelling, and proton conducting properties of the membranes were investigated in relation to their structures and compared with those of perfluorinated ionomer (Nafion 117). Films of SPAEENH copolymers in acid form all showed high thermal stabilities with glass transition temperatures (T g ) > 224°C and decomposition temperatures (T d ) > 264°C. In general, the SPAEENH copolymers exhibited low moisture absorption and in some instances high proton conductivities (from 10 -2 to 10 -1 S/cm) comparable to that of Nafion 117 at similar water uptake, swelling, and H 2 O/SO 3 H ratio.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. Monophenylated poly(ether sulfone)s (Ph-PES) and diphenylated poly(ether sulfone)s (DiPh-PES), were synthesized as starting materials for the preparation of sulfonated polymers with well-defined chemical structure. Mild post-polymerization sulfonation conditions led to sulfonated Ph-PES (Ph-SPES) bearing acid groups on both the pendant phenyl group and the backbone, and sulfonated DiPh-PES (DiPh-SPES) bearing acid groups only on the two pendant phenyl groups. Both series of polymers had excellent mechanical properties, high glass transition temperatures, good thermal and oxidative stability, as well as good dimensional stability. It is interesting to note that exclusively pendant-phenyl-sulfonated (bissulfophenylated) DiPh-SPES copolymers possessed obviously better thermal and oxidative stability compared with the corresponding pendant-phenyl-sulfonated/main-chain-sulfonated Ph-SPES copolymers. The methanol permeability values of the membranes were in the range of 7.0 Â 10 À7 -9.4 Â 10 À8 cm 2 /s at 30 C, which is several times lower than that of Nafion 117. DiPh-SPES-50 and Ph-SPES-40 also exhibited high proton conductivity (approximately 0.13 S/cm at 100 C).

A series of fluorenyl-containing sulfonated poly(aryl ether ether ketone ketone)s (SPFEEKK) were synthesized via aromatic nucleophilic substitution polymerization. The sulfonation content (SC) was controlled by the feed ratios of sulfonated and nonsulfonated monomers. Flexible and strong membranes in the sulfonic acid form were obtained from cast membranes in the sodium salt forms by treatment with acid. The thermal properties, water uptake, swelling ratio, water state, oxidative stability, proton conductivity and methanol permeability were investigated. All the polymers had proton conductivities greater than 1 × 10 −2 S/cm at room temperature, and the conductivity values of m-SPFEEKK-80 and p-SPFEEKK-80 were up to 1.86 × 10 −1 and 1.78 × 10 −1 S/cm at 100 • C. This series of polymers also possessed good dimensional stability in water and low methanol crossover.

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