Functionalized Polymeric Resins for High-Purity Separations of Rare Earth Elements

Rare earth elements play a crucial role in the modern economy; these materials are essential for many industrial applications including medical imaging, personal electronic devices, optical displays, lasers, and magnets. Rare earth elements are attractive raw materials for modern industries due to their distinct electronic properties, but their nearly indistinct chemical properties make them very difficult to separate from one another. The global supply of rare earth elements is dominated by Chinese production, which presents global supply-chain and supply-security issues, and areas around the most productive rare earth element mines are notorious for high levels of pollution. As global demand for rare earth elements increases, a need for decentralization of their production and an opportunity for establishment of more sustainable production and separation processes are apparent. Covalently functionalized crosslinked polymers are a promising class of materials for rare earth element separations. These materials are a natural marriage between molecular rare earth element extractants and ion-exchange resins. We will employ thiol-ene Click Chemistry for polymer functionalization; this chemistry is orthogonal to a wide range of functional groups, making it a powerful platform for materials discovery. The robust covalent ether thiol linkage between the polymeric backbone and the functional group should facilitate minimal leeching of the metal-binding functional group even under very harsh separation conditions (harsh organic solvents, acidic aqueous environments, etc.). In this Phase I project, discovery of materials for rare earth interelement separations will occur through the following four objectives: • Develop high-throughput analytical procedures for evaluating rare earth element separations, enabling low detection limits for assessing challenging separations • Prepare a library of targeted and exploratory covalently functionalized polymeric resins • Screen library of functionalized resins to identify structure-to-function properties and topperforming materials • Define commercialization path for top performing candidates Phase I of this project will establish key works flows for analysis of rare earth element separation performance. This, coupled with a significant material discovery effort, will enable commercialization strategies to be developed for top-performing resins. Structure-to-function trends will be identified to inform the design and synthesis of resins in future phases of this project. We expect that subtle changes in the functional group composition will be required to achieve optimal separation performance between the chemically indistinct rare earth elements.