Correlated exchange in recyclable polymers via multidimensional diffusion power spectra

Understanding molecular interactions in complex environments is essential for developing sustainable materials with tailored properties. To expedite chemical recycling of polymers, dynamics of these materials must be explored. Correlated movement between structurally distinct components within crosslinked polymers undergoing deconstruction to monomers maps chemical structures to network dynamics, providing unique insights into interactions of polymers in reactive chemical environments and their reactivity therein. Here, we construct an NMR experiment to detect frequency-correlated exchange, which informs on exchange processes between molecules in distinct dynamic regimes. This approach extends a modulated-gradient echo train to 3D, using a unilateral magnet as a low-cost portable sensor. Results link proximally diffusing molecular moieties in operando settings and resolve dynamics of multiple components in complex mixtures. We corroborate frequency-correlated exchange with simulated data and benchmark the technique using linear and crosslinked polymers as standards with known domains arising from topology. Notably, we found that exchange between two frequencies indicates mutually diffusing molecules between regimes of motional averaging, porous confinement, and network localization. These insights enable comprehensive assessments of the influence and extent of crosslinking on polymer deconstruction. We expect this approach to enable measurement of heterogeneous reactions and improve understanding of network dynamics in complex materials.