Synthesis and characterization of a novel graft polymer based hydrophobic polysulfone main chain and hydrophilic sulfonated polyvinyl alcohol side chain as proton exchange membrane for DMFC

Abstract

The current challenge with sulfonated aromatic polymer proton exchange membranes (PEMs) lies in their inability to enhance proton conductivity, mechanical strength and methanol resistance concurrently. To address this issue, a novel approach has been taken by synthesizing hydrophobic polysulfone grafted with hydrophilic sulfonated polyvinyl alcohol (PSU-g-SPVA) through Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. This graft polymer is then utilized as a modified material for PEMs in direct methanol fuel cells (DMFCs). The morphology of phase separation within the Nafion matrix is significantly influenced by the proportion of PSU-g-SPVA. Notably, the Nafion/PSU-g-SPVA-40 modified demonstrates superior alcohol resistance, with a methanol permeability rate of 2.32 × 10⁻⁷ cm²/s. Furthermore, due to its outstanding proton conductivity, the proton selectivity of this modified membrane is an impressive 10.9 × 10⁴ S s/cm³, which significantly surpasses that of the standard Nafion membrane at 2.82 × 10⁴ S s/cm³. Grafting techniques of hydrophobic main chain and hydrophilic side chains open up a new method for the blending of polymers with huge polarity differences.