Theoretical Insights into Cosolvent Effects in PET Glycolysis: A Multiscale Transport-Activation Mechanism

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Abstract
Despite extensive advances in polyethylene terephthalate (PET) depolymerization, the molecular-level mechanisms by which solvents and cosolvents regulate PET swelling, transport, and bond cleavage remain insufficiently understood. Herein, an integrated molecular dynamics (MD) and density functional theory (DFT) calculation was employed to systematically elucidate the roles of eight representative cosolvents─tetrahydrofuran (THF), 2-methyltetrahydrofuran (M-THF), 1,3-dioxolane (DOL), δ-valerolactone (DVL), cyclopentanone (CP), ethylene glycol (EG), anisole (AS), and benzyl alcohol (BnOH)─in PET solvation and degradation-related environments. Analyses of free-volume evolution, diffusion behavior, and electronic structure-derived descriptors capturing local polarity and orbital localization reveal pronounced solvent-dependent differences in chain relaxation, molecular mobility, and electronic activation pathways. Ether- and carbonyl-containing cosolvents primarily promote PET swelling and molecular transport by modulating local polarity and chain relaxation, whereas the protic cosolvent benzyl alcohol forms a dynamically reconfigurable, ethylene glycol-coupled hydrogen-bond network that enhances molecular mobility and stabilizes reactive oxyanion/transition-state structures. These distinct interaction modes give rise to computed differences in activation barriers, which elucidate the depolymerization mechanisms of different cosolvents. This study establishes a unified transport–activation mechanistic understanding and provides theory-guided principles for the rational design of efficient cosolvent systems for PET recycling.
Funding Information
  • Natural Science Foundation of Shandong Province (ZR2022MB141)

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