“…Several such approaches (e.g., polymer-enhanced ultrafiltration) use metal-chelating polymers to selectively bind and extract REEs. 3,4 Thus, quantifying metal binding thermodynamics in aqueous solution is critical, but the interactions among metal-ion, polymer, and water are complex. [5][6][7] To probe these complexities, the thermodynamics (DG, DH, and DS) of the polymer-metal interaction have been studied: Binding is entropy driven, suggesting the critical role of water in REE chelation.…”