Previous work on Nafion ® nanocomposite membranes used oxadiazole oligomer (ODF) to functionalize silica nanoparticle through silanation, the product of which then used as a filler. A simple solvent casting was used as a fabrication method to produce polymer film with different filler contents. In this work, thermomechanical properties of the polymer electrolyte membranes were studied by dynamic mechanic thermal analysis (DMTA). The composite membranes showed the β relaxation peak at 60-80 °C. As ODF-SiO 2 filler was dispersed in the matrix, the physical crosslinking brought about by the nanoparticles reduced chain mobility, increased the temperature of the β relaxation. Starting at 90 °C, the shoulder of α relaxation was observed and the α peak significantly broadened, as the amount of the filler increased. This could be explained by an extra facilitating factor, which is probably the gradual desorption of water trapped in the ODF-silica particles. The water further plasticized the matrix, replenishing the evaporating water clusters, and prolonging increased ion-hopping into higher temperature regions. Additionally, the morphology of the composites was investigated. SEM images showed that the membranes with 5 wt% filler had a good dispersion while agglomeration started to be observed at 10 wt% loading. Finally, the fuel cell with 5wt% loading composite was tested for polarization, which showed that the highest power density was 0.97 W cm -2 , an acceptable value for fuel cell application.
