Novel pyridine-based aromatic copolymers containing 4,4'-biphenol or hydroquinone groups in the main chain were synthesized and characterized as polymer electrolytes for proton exchange membrane fuel cells (PEMFCs). Depending on the copolymer composition and pyridine monomer content in most cases soluble and high molecular weight copolymers were obtained. Flexible membrane films were prepared by casting N,N-dimethylacetamide (DMA(c)) solutions of copolymers. H-1 NMR and size exclusion chromatography were used to characterize the structures of the copolymers. High glass transition temperatures (T(g)s) and decomposition temperatures (T(d)s) were observed using dynamic mechanical analysis and thermogravimetry, respectively. The oxidative stability of the membranes was examined with Fenton's test. The doping ability and the proton conductivity of the membranes were also studied and the new copolymers can be potential candidates as new polymeric electrolyte materials for proton exchange membrane fuel cells. Finally, membrane electrode assemblies (MEAs) were constructed and tested in 25 cm(2) Single cell at different temperatures showing promising performance.