Chlorine-Free Depolymerization of Commercial PMMA via Oxygen-Centered Radicals

Mid-chain depolymerization enables chemical recycling of conventional plastics with carbon-carbon backbones into high-purity monomers under mild conditions and without any weak bonds typically installed by controlled radical polymerization. However, current reports of mid-chain depolymerization either suffer from poor reaction yields or rely on an excess of chlorinated solvents to generate only a small fraction of chlorinated radicals with corrosive byproducts. Herein, we introduce a chlorine-free photothermal mid-chain depolymerization methodology, which proceeds through a distinct oxygen-centered radical pathway. In the presence of ppm concentrations of anthraquinone, an efficient photocatalyst, up to 97% monomer can be successfully regenerated, while varying the catalyst loading allows the depolymerization rate to be modulated on demand. Notably, a wide range of commercial materials, such as Plexiglas, acrylic tubes, and light guide plates, can undergo efficient depolymerization, while temporal control could also be demonstrated via iterative "on/off" cycles.