Formation of Proton-Conducting Polymer Additives Based on Sulfonated Crosslinked Polystyrene in Nafion Membranes

A method for the in situ modification of Nafion perfluorinated proton-conducting membranes with a polyelectrolyte based on sulfonated crosslinked polystyrene has been developed. The method is based on the radical copolymerization of styrene with divinylbenzene in situ in the transport channels of Nafion and subsequent sulfonation. The use of a mixed dimethyl sulfoxide–isopropanol solvent, which provides, on one hand, an effective swelling of the Nafion membrane and, on the other hand, the diffusion of nonpolar monomers into the hydrophilic transport channels of the membrane, makes it possible to obtain samples with a uniform distribution of the polyelectrolyte throughout the membrane thickness. The developed method provides a significant increase in the charge carrier concentration and the proton conductivity of the membranes.