Hydrocarbon hybrid membranes of PEG/PMA/MPTMS/SiO2 and PEG/PMA/MPTMS/SiO2/GA were fabricated with various amounts of SiO2 and glutaraldehyde by sol gel method. The composition of the hybrid membranes was examined by X-ray diffraction patterns, Fourier transform infrared (FTIR) spectra (FTIR-ATR) and proton nuclear magnetic resonance (NMR) techniques. The surface morphology of the cast membranes were analyzed by scanning electron microscopy. The conductivity values for all composites displayed a magnitude of 10(-3) S cm(-1), with greater improvements observed under conditions of various temperature and humidity. The proton conductivity of the composite membranes was measured at various temperatures at 50% RH using electrochemical impedance spectroscopy. In order to understand the proton conducting mechanism, the membranes were also subjected to conductivity measurement over wide RH range at 50 degrees C. It was observed that the hybrid membranes with glutaraldehyde additive as a crosslinking agent exhibited exceptionally high conductivity values at all RH conditions at 50 degrees C. The stable proton conductivity values at lower RH conditions indicate that the proton conduction mechanism is of diffusion type. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.