Composite membranes based on sulfonated poly(ether ether ketone) and imidazolium type ionic liquids were prepared and characterized as potential electrolytes for elevated-temperature anhydrous polymer electrolyte membrane fuel cell applications. Atomic force microscopy and electrostatic force microscopy revealed that the hydrophilic ionic domains were formed in the membrane and the ionic domains were connected by small ionic channels that facilitate proton transporting process. The formed composite membranes were thermally stable up to 340 degrees C. With the increase in temperature, the maximum ionic conductivity of the formed membrane reached 8.3 x 10(-3) S cm(-1) at 170 degrees C and under anhydrous conditions. (C) 2010 Elsevier B.V. All rights reserved.