New Proton Exchange Membranes with Low Methanol Permeability for Direct Methanol Fuel Cells

The purpose of the proposed BMDO Phase II program is to develop and commercialize ion-conducting thermally stable polymers for use as high temperature proton exchange membrane/membrane electrode assembly (PEM/MEA) materials with low methanol permeabilityas components of direct methanol fuel cells (DMFC). Polymer electrolyte/proton exchange membrane (PEM) fuel cell systems are an environmentally friendly power source for a wide range of applications that include transportation, stationary powergeneration, and consumer electronics. Sulfonated ion-conducting sites have been introduced via direct polymerization, allowing control of both their location and concentration. Preliminary work during the Phase I research program has indicated that the PIand colleagues are capable of synthesizing such materials exceeding the conductivity and methanol permeability performance of perfluorinated sulfonic acid Nafion materials at, or above, room temperature. These new sulfonated copolymers show no change incell resistance over a period of one month under fully humidified conditions. Additionally, cast films of the novel copolymers demonstrated a marked (nearly fourfold) decrease in methanol permeability, which could greatly limit flooding, and the decreasedefficiency associated with this phenomenon. These new materials also are much less costly than fluoropolymers and they can be synthesized from commercially available starting materials.