Sulfonated and Carboxylated Copoly(Arylenesulfone)S for Fuel Cell Applications

Summary

New functional copoly(arylenesulfone)s have been prepared by Ni(0)-catalyzed coupling copolycondensation. Incorporation of functionalities was achieved either by polymerization and subsequent functionalization (SO ₃ H groups) or by polymerization of already functionalized monomers (COOH groups). For the first time it was shown that these materials are promising for fuel cell applications.

While for the polyarylenesulfone copolymers there is a range of copolymer composition that leads to soluble materials (the homopolymers are insoluble), all ester copolymers (ME, SE) are soluble. For ME only oligomers are observed, the system SE led to higher molecular weights, but whereas we were able to adjust copolymer composition, control over molecular weights was limited. Functionalization both with sulfonic and carboxylic acid groups resulted in novel polyelectrolytes with good thermal and mechanical properties.

Further investigation concerning the suitability of these materials for fuel cell applications showed that carboxylic acid functionalities in poly(arylenesulfone) blends led to reduced swelling behavior in water, but methanol permeation increases. Therefore COOH functionalized membranes are not applicable for the DMFC. Further measurements on hydrogen and oxygen permeabilities are in progress. The respective results have to be correlated with ionic conductivities and the electro-osmotic drag of water.