Photo-initiated solvent-mediated depolymerization of consumer poly(methyl methacrylate) without chlorinated reagents

Abstract

Abstract The chemical recycling of commodity acrylic polymers, such as the transparent thermoplastic polymethyl methacrylate (PMMA), typically requires temperatures of 350-400°C. Herein, we report chemical recycling back to monomers for PMMA between 120-180°C, through UV illumination under oxygen-free conditions. We have achieved gram-scale degradation of consumer plastic with >95% conversion, yielding >70% monomer, which can be readily repolymerized. The process proceeds even at high concentrations (>1 M) and depends strongly on solvent choice: aromatic solvents like dichlorobenzene and diphenyl ether maximize conversion. In contrast to a concurrently published study, we report that chlorine radicals are not required for depolymerization; however, when present, they react with the unzipping chain to form chlorine-functionalized PMMA which can be upcycled through derivatization. In more sustainable non-chlorinated solvents such as benzonitrile, minimal termination by radicals enables complete unzipping. These findings demonstrate a low-temperature, scalable route for the chemical recycling of PMMA, offering alternative pathways for plastic circularity.