Enlightening the Depolymerization Kinetic Mechanism in Reversed Atom Transfer Radical Polymerization via In Silico Modeling

Reversed atom transfer radical polymerization (ATRP) is a promising polymer recycling method that enables the depolymerization of vinyl polymers with functional end groups back to monomers with high yield. Despite significant progress, the kinetic understanding of the reversed ATRP process remains limited. In this work, kinetic features and phenomena of the reversed ATRP are revealed by in silico modeling for the first time. The model successfully captures kinetic data of the depolymerization of iron-catalyzed bromine-terminated polymethacrylates reported by the Anastasaki group. Importantly, the use of the as-developed model enables rationalization of the kinetic mechanism through reproducing distributional properties, accounting for the effect of end-group fidelity of initial polymers and bias of molar mass distribution (MMD) determination through off-line gel permeation chromatography (GPC) analysis. Importantly, a thermodynamically driven chain equilibrium that can result in a bimodal chain length distribution as depolymerization progresses is found through kinetic simulations and mathematical proofs. This work helps us deeply understand the kinetics of reversed ATRP and provides mechanistic cues for designing chemical recycling by this process.