To prepare a cross-linked hybrid proton exchange membrane with high mechanical and oxidative stability, a silane monomer, namely 3-glycidoxypropyltrimethoxysilane (KH-560), is first grafted to sulfonated poly(arylene ether ether ketone)s bearing carboxyl groups (SPAEK-C) and hydrolysis-condensation is then performed on the grafted membranes to make them cross-link. H-1 NMR measurements and Fourier transform infrared spectroscopy are used to characterize and confirm the structures of SPAEK-Cs and hybrid polymer electrolyte membranes, respectively. The Si-O-Si cross-linking structure enhances the stability of the PEM greatly. The proton conductivities of the hybrid membranes with 5% KH-560 in weight reach 0.155 S cm(-1) at 80 degrees C which is comparable to that of Nafion (R) membranes. The ion-exchange capacity. water uptake and swelling, methanol permeability. mechanical properties are investigated to confirm their applicability in fuel cells. (C) 2009 Elsevier B.V. All rights reserved.