Novel aromatic polyethers bearing polar pyridine units 0 along the main chain and side cross-linkable propenyl groups have been successfully synthesized. Their properties relating to their ability to be used as polymer electrolyte membranes for high temperature fuel cell applications, were thoroughly investigated. Cross-linked membranes were obtained by thermal curing of the cross-linkable polymers with the use of a bisazide as the cross-linking agent. The glass transition temperatures of the cross-linked membranes were determined by dynamic mechanical analysis and found to be higher compared to the neat polymers proving the successful cross-linked network. The doping ability in phosphoric acid and the proton conductivity of the cross-linked membranes were higher compared to the noncross-linked analogues. Finally, membrane electrode assemblies (MEAs) were constructed and tested in a single cell at temperatures between 180 and 220 degrees C. The superior performance of the cross-linked membranes in combination with the operating stability at 200 degrees C for 48 h demonstrate the potential use of these materials as electrolytes for high temperature PEM'fuel cells.