Organic/inorganic composite membranes for direct methanol fuel cell (DMFC) application were prepared with sulfonated poly(ether ether ketone) (SPEEK) and layered silicate such as organic-montmorillonite (OMMT) by solution intercalation technique. Through organically modification, the hydrophilic MMT was made organophilic and therefore was compatible with conventional organic polymers. The result of X-ray diffraction (XRD) shows that the interlayer spacing of MMT in the SPEEK matrix exceeds 5.88 nm and the polymer chains of SPEEK have diffused into the MMT galleries. The methanol permeability of the SPEEK/OMMT composite membranes decreases significantly. At the same time, the composite membranes show 1.2 x 10(-2) S/cm proton conductivity at 90 degrees C, which approaches the value of Nation (R) 115. As a result, SPEEK/OMMT composite membranes offer a low-cost alternative to the perfluorinated membranes. (c) 2005 Elsevier B.V. All rights reserved.