Phosphonic acid grafted bis(4-γ-aminopropyldiethoxysilylphenyl)sulfone (APDSPS)-poly(vinyl alcohol) cross-linked polyelectrolyte membrane impervious to methanol

A new monomer precursor, bis(4-γ-aminopropyldiethoxysilylphenyl)sulfone (APDSPS), has been synthesized and cross-linked poly(vinyl alcohol) (PVA)-APDSPS composite polyelectrolyte membranes with phosphonic acid functionality were prepared by acid-catalyzed sol–gel method, as a suitable alternative to perfluorinated membranes for the polyelectrolyte fuel cells applications. Phosphonic acid functional groups showed high intrinsic proton conductivity due to high mobility of protonic charge carriers and degree of self-dissociation, in the polymer matrix. Cross-linking was carried out by gluteraldehyde to achieve micro-tailoring in hydrophobic domain for polyelectrolyte membranes impervious to methanol. These membranes were designed to possess all the required properties of proton conductive membrane, namely reasonably swelling, good mechanical, dimensional and oxidative strength, flexibility, low methanol permeability along with reasonable proton conductivity due to bridged aromatic sulfone between functionalized silica. Higher thermal activated conduction process for synthesized membranes in comparison to Nafion 117 (N117) was responsible for slightly higher energy of activation for proton transfer. Moreover, from the estimation of selectivity parameter, 60% APDSPS composition among the PVA-APDSPS composite membranes showed highly suitable polyelectrolyte membrane, which suitability increased with the temperature.