Novel aromatic polyether type copolymers bearing side chain polar pyridine rings as well as combination of main and side chain pyridine units have been evaluated as potential polymer electrolytes for proton exchange membrane fuel cells (PEMFCs). The advanced chemical and physicochemical properties of these new polymers with their high oxidative stability, mechanical integrity and high glass transition temperatures (T(g)'s up to 270 degrees C) and decomposition temperatures (T(d)'s up to 480 degrees C) make them promising candidates for high and medium temperature proton exchange membranes in fuel cells. These copolymers exhibit adequate proton conductivities up to 0.08 S cm(-1) even at moderate phosphoric acid doping levels. An optimized terpolymer chemical structure has been developed, which has been effectively tested as high temperature phosphoric acid imbibed polymer electrolyte. MEA prepared out of the novel terpolymer chemical structure is approaching state of the art fuel cell operating performance (135 mW cm(-2) with electrical efficiency 45%) at high temperatures (150-180 degrees C) despite the low phosphoric acid content (<200 wt%) and the low platinum loading (ca. 0.7 mg cm(-2)). Durability tests were performed affording stable performance for more than 1000 h. (C) 2011 Elsevier B.V. All rights reserved.