Designing a New Ionomer from Scratch - Pushing Polypoms to the Limit James L. Horan, a Mei-Chen Kuo, a Sonny Sachdeva, a Hui Ren, c Andrew S. Perdue, a Steven F. Dec, b Michael A. Yandrasits, d Steven J. Hamrock, d Matthew H. Frey, c and Andrew M. Herring. a a Department of Chemical Engineering, Colorado School of Mines, Golden, Colorado 80401, USA b Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado 80401, USA c 3M Corporate Research Materials Laboratory, 3M Center Bldg., St. Paul, MN 55144, USA d 3M Fuel Cell Components Program, 3M Center, St Paul, MN 55144, USA We have fabricated proton conducting films using monomers based on vinyl substituted silicotungstic acid heteropoly acids (HPAs) and acrylate co-monomers. In this work we probe the limits of this system based on increasing the weight loading of the HPA to 85 wt%. Although impressive proton conductivities can be achieved with these films under hotter and drier operating conditions than in conventional proton exchange membranes, the materials have mechanical limitations. We show that very different film morphologies can be prepared based on whether or not the film is polymerized thermally or by UV light. In general the UV cured films have superior proton conductivity, but have a linear morphology resulting in a brittle film. The thermally cured films have a clustered morphology with good mechanical attributes but have poor proton conductivity. Introduction Proton exchange membrane (PEM) fuel cells are still the most desirable component of future zero emission, high efficiency automobiles. However, their unit cost, ease of operation, and reliability must be reduced which includes eliminating the humidifier from the fuel cell system. Currently the commercial proton exchange membrane (PEM) is fabricated from a perfluorosulfonic acid (PFSA) polymer such as Nafion ® . Unfortunately PFSA ionomers must be fully hydrated to achieve their maximum proton conductivities and practical levels of proton conductivity can only be achieved in vehicles operating at an inlet RH of 80% which still necessitates the use of a humidify and undesirable complex water management and recovery. To achieve the goal of a PEM that can operate at temperatures from freezing to 120ºC using dry inlet gases it will be necessary to develop new PEMs that are based new chemistries. The heteropoly acids (HPAs) are a class of inorganic oxides that have some of the highest solid state proton conductivities known at room temperature, although the actual proton conductivity achieved depends strongly on the hydration state of the HPA (1, 2). In previous work we have shown that the HPAs have very high proton conductivities at room temperature and can be operated at ambient conditions in a fuel cell using dry gases (3). Importantly we demonstrated that some of the protons in HPA have very impressive ECS Transactions, 25 (1) 1101-1107 (2009) 10.1149/1.3210663 ©The Electrochemical Society 1101 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 140.114.114.18 Downloaded on 2014-10-14 to IP