Functionalized zeolite was synthesized by using 1,3-propane sultone as a functionalization agent of sulfonic acids to improve the proton transport properties for high temperature (120 degrees C) proton exchange membrane fuel cells (PEMFCs). The composite membrane is developed by incorporating varying ratios of sulfonated zeolite into sulfonated poly(arylene ether sulfone) (SPAES) copolymers. The sulfonated zeolite is expected to enhance proton conductivity and mechanical properties. The SPAES copolymer is synthesized by direct polymerization and has 50 degrees of sulfonation. In this study, the proton conductivity, mechanical properties, and unit cell operating test of the composite membrane are investigated and compared with those of pristine membrane. The composite membrane containing 5 wt.% sulfonated zeolite increases proton conductivity from 0.022 S/cm to 0.030 S/cm at 120 degrees C and 50% relative humidity condition. For the single cell test, the developed composite membrane with 5 wt.% sulfonated zeolite exhibits a notable power density (54% increase) for high temperature PEMFC applications. (C) 2012 Elsevier B.V. All rights reserved,