AbstractPolymer composite membranes based on sulphonated polymers, such as sulphonated poly(ether ketone) and sulphonated poly(ether ether ketone), and silicates were prepared and characterized for water/methanol permeabilities and proton conductivity studies. The study showed methanol and water permeability in the composite system decreased, with respect to the plain polymer/ionomer, with the increase in content of silicates. The permeability reduction in the composite membranes is discussed using models and theories. It was also found that the proton conductivity of the ionomer-composite membranes increased with the increase in total ﬂux of the system, emphasising a good correlation
between the total ﬂux of the composite membranes and proton conductivity. The work clearly demonstrates that the same transport mechanism governs both methanol–water crossover and proton conductivity in these polymer
electrolyte composite membranes.