Proton exchange membrane fuel cells (PEMFCs) are considered efficient, environmentally friendly power sources. However, there are no commercially available hydrocarbon-based proton exchange membrane (PEM) capable of achieving the DOE?s 2020 technical targets, some of which include 0.02 ?.cm<
sup>
2<
/sup>
area specific proton resistance at maximum operating temperature and water partial pressures from 40-80kPa, durability of 20,000 cycles (Mechanical), >
500Hours (Chemical), and 20,000 cycles without 20% loss in OCV (Chemical and Mechanical), maximum operating temperature of 120�C, and $20/m<
sup>
2<
/sup>
(at 500,000 systems/year). While significant progress has been made over the previous two decades in the development of polymer electrolytes for fuel cells, their widespread commercialization has been largely hindered by the high-cost and low-durability. NanoSonic has developed novel, cost-effective, quaternary ammonium- functionalized hydrocarbon ionomers doped with phosphoric acid as intermediate temperature (120�C) PEMs for fuel cells as energy efficient transportation alternative to internal combustion engines. These next-generation polymer membranes possess excellent film forming and mechanical properties, exceptional hydrated dimensional stability, have good proton conductivity at low relative humidity (RH) and exhibit superb stability over current state of the art perfluorosulfonic acid (PFSA) ionomers used under the harsh operating conditions of PEM fuel cells. NanoSonic?s engineered and manufactured a library of membrane types, identified a subset of best performers, and are evaluating these materials in partnership with Los Alamos National Laboratory. Membrane electrode assembly (MEA) fabrication was successfully demonstrated in during Phase I. Initial results utilizing these novel polymer membranes and non-optimize MEAs generated during this project demonstrate good proton conductivity at 80-200�C at zero humidification (RH=0%) and have notably low high frequency resistance (HFR). NanoSonic?s membranes show superior acid retention in comparison to the reference doped PBI membranes, an attribute credited to the formation of stable ionic acid pairs, in addition to polar nteractions with the polymer backbone.