Nafion-MPMDMS nanocomposite membranes with low methanol permeability

In this work Nafion nancomposite membranes have been synthesised using a directed sol–gel synthesis technique with (3-mercaptopropyl) methyldimethoxysilane as the silicon alkoxide precursor. The resulting membranes with 16.7 wt% inorganic content showed a 89% reduction in methanol permeability compared to Nafion 117 at 50 °C. Small angle X-ray scattering data profiles for the nanocomposite membranes were distinctly different to those of unmodified Nafion 117 and showed a distinct upturn at low q. The slope of the curves was approximately −3.5 over the range 0.01 < q < 0.015, suggesting the presence of scattering objects with a mass fractal structure in the range 40–60 nm. Such objects were directly observed by transmission electron microscopy, and indicate an interpenetrated network of inorganic agglomerates and the host Nafion polymer, which significantly decreases the methanol permeability. The membranes may be suitable candidates for use in direct methanol fuel cells.