Systematic Control of the Crystalline Morphology in Perfluorosulfonate Ionomer Membranes

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CBET-0756439MooreThis fundamental project is aimed at filling a critical void in our understanding of the form and function of polymeric crystals produced by the ordered packing of backbone chains in modern fuel cell membranes. While we have learned a great deal about the organization of the proton-conducting ionic domains in functional polymers such as the perfluorosulfonate ionomer (PFSI) Nafion, it is remarkable that we know very little about the detailed structure and formation of the crystallites in these materials or the spatial arrangement of these ordered features with respect to the proximity of the ionic domains. In contrast to the vast majority of morphological studies of these technologically important polymers, this project will be focused on the ?other? important morphological feature in these membranes, namely the critical significance of the crystalline component. The experimental approach in this project will involve (1) development and refinement of methods to systematically control the degree and organization of crystallinity in PFSIs, (2) structural characterization of the crystalline component, and (3) analysis of the fuel cell relevant properties impacted by the crystalline order. With a controlled range of crystallinities provided by tailored membrane processing and new, highly crystalline PFSIs currently available with shorter functional sidechain structures, we will be able to finally isolate the specific contributions of this attribute in membrane performance/durability and allow a comprehensive understanding of the morphological factors that lead to efficient energy conversion in proton exchange membrane fuel cell (PEMFC) applications. This research will impact fundamental modifications to the conventional processing parameters used for PFSI membranes that focus on the development of more ordered crystalline domains, and stimulate a multi-disciplinary approach to membrane design and fabrication. From a societal impact perspective, it is anticipated that fundamental research in this specific area will enable a more efficient, robust, and sustainable energy conversion with low environmental impact. Students involved in this project will be exposed to state-of-the-art methods of morphological characterization, engineering aspects of membrane fabrication, and the modern technology of fuel cell science. Educational modules developed in the course of this work will be incorporated in the expanding energy curriculum of the Science and Engineering programs at Virginia Tech.