Depolymerization of Commercial Polymethacrylates Triggered by Hydroperoxides

Abstract

The chemical recycling of poly(methyl methacrylate) (PMMA) and related polymethacrylates is challenging due to the all-carbon backbone, which resists thermal and chemical degradation under mild conditions. Existing depolymerization strategies either require modification of the PMMA structure or rely on photochemical activation, limiting versatility and practical scalability. Herein, we report a thermally driven, hydrogen-atom-transfer (HAT)-initiated depolymerization of unmodified commercial polymethacrylates. Simple hydroperoxides, tert-butyl hydroperoxide (TBHP) and cumene hydroperoxide (CHP), serve as radical precursors, requiring no photoactivation, no specialized chain ends, and no chlorinated solvents. At elevated temperatures, oxygen-centered radicals are generated and abstract hydrogen atoms from the polymer chains. This triggers β-fragmentation and initiates chain unzipping. At 220 °C with 10 mol % TBHP, 30% of the polymer remained, indicating 70% depolymerization. However, only 55% was in the form of intact monomer, and 15% was consumed by side reactions during long exposure to high temperature. This approach was extended to poly(butyl methacrylate), poly(benzyl methacrylate), and poly(phenyl methacrylate), and demonstrated moderate tolerance to ambient oxygen levels. These results establish thermally triggered HAT depolymerization as a simple approach for the depolymerization of commercial polymethacrylates.