Proton conducting membranes based on cross-linked sulfonated poly(ether ether ketone) (SPEEK)

A new method for the preparation of proton exchange membranes (PEMs), based on cross-linked sulfonated poly(ether ether ketones) is reported. The cross-linking involves thermally activated bridging of the polymer chains with polyatomic alcohols, which makes the polymer mechanically stronger and reduces its swelling by water. Although the cross-linking occurs through the sulfonic acid group, a major portion of acid functions is not involved in cross-linking and remains available for proton transfer. Owing to this, membrane conductivities are only somewhat reduced, leaving some with values above 2×10−2 S/cm at room temperature.