From Rare-Earth Extraction to Polymer Recycling: Innovations in Materials for Sustainability

The transition to a sustainable future requires innovative approaches in materials design, utilization, and recycling. In this talk, I will discuss two advancements at the intersection of polymer chemistry and sustainability: the development of metal-chelating polymers for rare-earth element (REE: La–Lu, Y, and Sc) extraction, and the synthesis of chemically recyclable polymers.

First, I will present our work on polymers for the selective chelation of REEs, which are critical elements in many green energy technologies. As REE demand rises, more efficient extraction and purification methods are needed. Metal-chelating polymers offer an attractive solution due to their low cost and high affinity for target metals. However, little is understood about how polymer architecture influences metal binding. To address this gap, we synthesized a series of metal-chelating polymers and investigated the thermodynamics of binding using isothermal titration calorimetry. By elucidating the thermodynamic profile of each chelating material, we have gained insight into each material’s properties as a metal chelator.

In the second half, I will present the synthesis of chemically recyclable copolymers based on (1, n′-divinyl)-oligocyclobutane (DVOCB(n)). DVOCB(n) is synthesized from the Fe-catalyzed [2+2]-cycloaddition of butadiene, a commodity monomer, and is semicrystalline. Using commercially available all-hydrocarbon monomers, we developed a tandem ring-opening metathesis polymerization (ROMP)–acyclic diene metathesis (ADMET) approach which enabled the synthesis of materials with systematic variations in DVOCB(n) hard-segment length and content. By tuning the DVOCB segment length and content, we were able to access a broad spectrum of tunable melting temperatures and rubbery plateau moduli. Finally, ethenolysis of these copolymers was demonstrated and pristine DVOCB(n) recovered, thus offering a potential end-of-life circularity for these materials.

Together, these advancements offer promising solutions for improving rare-earth element recovery and promoting the circularity of polymer materials.