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Photo-Initiated Depolymerization of Consumer Poly(methyl methacrylate): Chlorine Not Required
Summary
Researchers developed a low-temperature chemical recycling method for poly(methyl methacrylate) (PMMA) that uses UV illumination at 120-180 degrees C to depolymerize the acrylic polymer back to monomer, eliminating the need for chlorine and drastically reducing the 350-400 degrees C temperatures required by conventional thermal recycling.
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 new pathways for plastic circularity.
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