Chemical Recycling of Thiol Epoxy Thermosets via Light-Driven C-C Bond Cleavage

Epoxy thermosets are high-volume materials that playa centralrole in a wide range of engineering applications; however, technologiesto recycle these polymers remain rare. Here, we present a catalytic,light-driven method that enables chemical recycling of industriallyrelevant thiol epoxy thermosets to their original monomer at ambienttemperature. This strategy relies on the proton-coupled electron transfer(PCET) activation of hydroxy groups within the polymer network togenerate key alkoxy radicals that promote the fragmentation of thepolymer through C-C bond beta-scission. The method fullydepolymerizes insoluble thiol epoxy thermosets into well-defined mixturesof small-molecule products, which can collectively be converted intothe original monomer via a one-step dealkylation process. Notably,this process is selective and efficient even in the presence of othercommodity plastics and additives commonly found in commercial applications.These results constitute an important step toward making epoxy thermosetsrecyclable and more generally exemplify the potential of PCET to offera more sustainable end-of-life for a diverse array of commercial plastics.