ABSTRACT

Polymer membranes would potentially benefit many sectors of the U.S. economy, including manufacturing, chemicals production, healthcare, and defense, by removing contaminants from various process streams. However, the materials needed to make these membranes lack the efficiency, productivity, and stability that is often required for current and emerging applications. To fill this gap and provide broad opportunities for growth in various sectors of the U.S. economy, fundamental research is needed to develop new materials design strategies. This proposal focuses on a unique class of polymers that have fluorine covalently attached to their structure. Unlike all other known polymers, these fluoropolymers have theoretically unexpected and beneficial abilities to separate contaminants from various products. To uncover the reason behind these abilities, a series of polymers with varying amounts of fluorine will be characterized to reveal the role of fluorine on enhanced efficiency, productivity, and stability for membrane-based separations. Additionally, this proposal will develop the Polymer Prodigies program to connect undergraduate and graduate students from MIT with high school and middle school students who are underrepresented in science and engineering. This program will involve in-person lectures and hands-on experiments related to polymers, providing relevant connections between these experiments and molecular separations. Curriculum developed for this program will also be recorded as videos and disseminated through online platforms to promote broader engagement. Finally, this proposal seeks to attract a new generation of researchers to the field of separation science through collaboration with the MIT UROP program, MIT ACCESS Program, and NetPals. Through the UROP program, specific efforts will be made to bolster opportunities for female students and underrepresented minorities in research projects for this proposal.

Unlike other nonpolar molecules, perfluorinated molecules do not obey thermodynamic mixing theories when combined with non-fluorinated species. This breakdown in theory has important implications for membrane-based gas separations. For certain industrially relevant gas pairs, perfluoropolymers have the best combinations of permeability and selectivity of all known polymers, and these materials also exhibit unprecedented stability to physical aging and a resistance to plasticization. However, the origins of this theoretical anomaly are not well understood. Therefore, the main consideration of this proposal is to investigate the role of fluorine on membrane separation performance. To accomplish this goal, this project will leverage strategies in macromolecular synthesis to design glassy polymers of high molecular weight with varying amounts of fluorine appended to the backbone of the polymer. These efforts will be complemented with advanced materials and transport characterization, and findings will be interpreted through theory and simulations. By doing so, hypothesis-driven questions will be tested to investigate why fluorine unexpectedly increases selectivity, reduces physical aging, and improves plasticization resistance for membrane-based gas separations. From a broader perspective, this proposal seeks to publish peer-reviewed papers on reference materials and reference standards to enable more robust measurement techniques within the membrane community.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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