Diffusion power spectra as a window into dynamic materials architecture

Chemical recycling of commodity and specialty polymers presents a multifaceted challenge for industrial societies. On one hand, macromolecular architectures must be engineered to yield durable products that, on the other hand, rapidly deconstruct to recyclable monomers under pre-determined conditions. Polymer deconstruction is a chemical process that requires deep understanding of molecular reactivity in heterogeneous media, where porous material architectures evolve in both space and time. To build this understanding, we develop herein experimental and analytical methods describing sets of diffusive eigenmodes that exist within time-varying, non-Euclidean boundary conditions—a situation commonly encountered in the reactive deconstruction of polymers where chain fragments splay, alter their local dynamics, and evolve in their confinement of reacting media. Diffusion power spectra, discerned experimentally by NMR, yield polymer and solvent frequency-domain velocity autocorrelation functions that are analyzed in the context of physical models for chemical reactions parameterized with fractal mathematics. The results connect local motion in polymers to chemical reactivity during acidolysis of circular elastomers.

Methods
This dataset includes MGSE data from experiments performed with a PM 25 NMR-MOUSE interfaced to a Kea II spectrometer using Magritek's Prospa software. Samples and methods are described in the Materials and Methods section of the corresponding manuscript, "Diffusion power spectra as a window into dynamic materials architecture." For each MGSE experiment, transient CPMGs are contained in folder titled with the total time for each echo train; subfolders are titled with the number corresponding to N_echoes, where the number denotes the number of echoes. Within these folders, the raw echo train data and corresponding time vector are contained in a file named "data.csv."