Novel nanocomposite proton exchange membranes were prepared by using sulfonated mesoporous silica nanoparticles (SMSNs) as inorganic fillers through direct blending with sulfonated polyimides (SPIs). The microstructure and properties of the resulting hybrid membranes were studied. The SMSNs with a diameter of 50-300 nm exhibited the ordered mesopores of about 2.3 nm. The introduction of sulfonated mesoporous silica improved the thermal stability, water uptake and methanol permeability of the resulting nanocomposite membranes as compared with SPI. The hybrid membrane with 3 wt% SMSNs showed the highest water-uptake value of 54.2% and lowest methanol permeability value of 5.23 x 10(-6) cm(2) s(-1). When the content of SMSNs was higher than 3 wt%, both the values decreased slightly because of the aggregation of SMSNs. All of the membranes showed the excellent proton conductivity as compared with Nafion 117. When 7 wt% SMSNs were incorporated into the SPI, the membrane sample presented the highest proton conductivity at different testing temperatures, indicating that the addition of SMSNs can also improve the proton conductivity of composite membranes. (C) 2010 Elsevier B.V. All rights reserved.