Proton-conducting polymer membrane comprised of a copolymer of 2-acrylamido-2-methylpropanesulfonic acid and 2-hydroxyethyl methacrylate

In order to identify a proton-conducting polymer membrane suitable for replacing Nafion® 117 in direct methanol fuel cells (DMFC), we prepared a cross-linked copolymer of hydrophilic 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and 2-hydroxyethyl methacrylate (HEMA). Fumed silicas were also added in an attempt to increase the amount of water adsorbed by the membrane and to enhance water retention. Hydrated copolymer membranes adsorbed significantly more water than Nafion® 117, but were no better at retaining water during drying under ambient conditions. Films composed of 4% AMPS—96% HEMA had a room temperature proton conductivity of 0.029 S cm−1, which increased to 0.06 S cm−1 at 80 °C.