Engineering Selective Fuel Cell and Water Treatment Membranes

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0932740WangProject SummaryMembranes with controllable separation properties play a vital role in advanced energy and environmental applications. Underlying mechanisms and structure-property relationships that promote permselectivity have been explored in great detail for polymer membranes that separate gas molecules, but for polymers that contain attached ionic groups and absorb water, such as fuel cell membranes, the underlying molecular concepts of why selectivity exists in these systems and how selectivity can be enhanced through rational molecular design are not clear. The fundamental difference between gas separation membranes and water-absorbing membranes is that the transport processes in gas separation membranes are dominated by the polymer dynamics where the water-absorbing membrane transport properties are dominated by the motion of water within the relatively stationary polymer matrix. Therefore, this project will focus on the critical role of water-polymer interactions and water binding and diffusion within the chemical and physical framework of the polymer. Intellectual Merit: The central theme of the proposed research is to study a system of end-linked polymers that contain sulfonate groups and to determine the critical molecular parameters for designing fuel cell and nanofiltration membranes with tunable selectivity for water, ions, and small molecules. The tailored materials with well-controlled structural variation will advance our fundamental understanding of the different routes to increasing selectivity in sulfonated polymers. The characterization tasks will be intimately integrated with the synthetic efforts to probe how the molecular characteristics of the membrane influence binding and diffusion of water, and in turn how the water properties influence the transport of ions and small molecules. An in-depth study of membrane and transport properties on the molecular, multi-nanometer, and membrane length scales will be performed using a combination of spectroscopy, morphological analysis, and transport measurements, with special attention paid to the chemical and physical framework and the water binding within the membrane. By combining both fundamental insights and performance-specific transport measurements, a complete picture of molecular structure-transport properties can be formed for these important materials.Broader Impacts: The success of this project will open a completely new direction in the development of ion-containing membranes and has profound implications for rational design of nanostructured membranes with new architectures and superior selectivity and transport properties. Future scientists capable of working in the interdisciplinary field of polymer membranes and fuel cells will be trained and educated within this program. Undergraduates and minorities will be integrally involved in the research program. The "Materials + Creativity + Community = Energy" modules including lecture materials, handouts, slides, and hand-on experimental demonstrations will be created and deployed in campus open houses, during student group activities on and off campus (seminars, student club gatherings, high school visits), and during two new summer residential camps including Penn State Science Workshop for grades 9-12 teachers and ASM Materials Camp for high school students.