Fabrication of a polymer electrolyte membrane with uneven side chains for enhancing proton conductivity

Construction of effective proton transport channels in proton exchange membranes is the key to the design of high performance proton conductive materials. Enhancement of proton conductivity of polymer electrolyte membranes was achieved by broadening the proton transfer channels via attaching acid groups to both long and short side chains of polymer electrolytes simultaneously. To demonstrate the effectiveness of the uneven side chains on the conductive properties of polymer membranes, three types of polyamide based electrolyte membranes with long side chains, short side chains and long/short side chains were prepared. It was found that among the three types of membranes with the same ion exchange capacity (IEC) value, the one with uneven side chains exhibits the highest proton conductivity. An increase of the IEC value in the uneven side chain membrane leads to a significant increase of proton conductivity. The study provides useful insight into the structural design of polymer electrolyte materials with high conductivity for fuel cell applications.