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In this study, a three-dimensional off-lattice kinetic Monte Carlo-Molecular Dynamics (KMC-MD) simulation framework [Comp. Mat. Sci. 229, 112421 (2023)] is used to investigate the dehydrochlorination/conjugation transformation of polyvinyl chloride (PVC) in sodium hydroxide (NaOH) with atomistic resolutions at experimental timescales (103 – 106 s). Our framework enables an examination of the competing reaction pathways and molecular-scale changes influenced by various solvents (acetone, ethylene glycol, triethylene glycol, tetrahydrofuran, and bio-derived solvents), as well as the influence of varying molecular weight distributions, NaOH concentrations, and temperatures. The algorithm simulates bond cleavage and formation during the KMC stages, whereas the MD stage is dedicated to the relaxation and thermalization of the PVC-NaOH-solvent system. The framework allows us to capture important configurational aspects (mixing, correlations, clustering, etc.) that are not accessible with a traditional microkinetic model, and it potentially allows us to perform benchmarking at experimental timescales. 

The drive towards a circular economy in plastic materials has become a worldwide goal. 

In our prior study [Olowookere, F. V.; Turner, C. H. J. Phys. Chem. B 2023, 127(42), 9144–9154], we introduced a new scaling relationship to predict gas solute diffusion at challenging conditions, focusing on CO2 and SO2 diffusion in multivalent ionic liquid (IL) solvents. This work extends our initial exploratory study into a much broader array of systems, encompassing additional solutes (N2, CH4, C2H6, C3H8, C3H8O, and H2O) and a variety of different ionic liquid species ([Bzmim3]3+, [Bzmim4]4+, [BMIM]+, [EMIM]+, [HMIM]+, [NapO2]2–, [BzO3]3–, [BF4]−, [Tf2N]−, and [PF6]−). Our study demonstrates a remarkably robust logarithmic correlation between solute diffusion and solvent accessible surface area (SA) across 20 different additional systems. We perform comprehensive analyses of the underlying molecular phenomena responsible for this correlation, including solute lifetime distributions, void space dynamics, and Voronoi tessellation, in order to elucidate a stronger mechanistic understanding of this behavior. Our findings highlight a direct link between the solvent accessible SA and the size of the void domains. Overall, our scaling approach provides an efficient and reliable approach for predicting diffusion from analyses of short simulations at higher temperatures.