Oxygen-Tolerant ATRP Depolymerization Enabled by an External Radical Source

Abstract

Although the chemical recycling of polymers synthesized by controlled radical polymerization enables the recovery of pristine monomer at low temperatures, it operates efficiently under strictly anaerobic conditions. Instead, oxygen-tolerant depolymerizations are scarce, and are either restricted to the use of a boiling co-solvent or are performed in closed vessels, often suffering from low conversions. Here, an open-vessel, oxygen-tolerant depolymerization of atom transfer radical polymerization (ATRP)-synthesized polymers is introduced, leading to high percentages of monomer regeneration (>90% depolymerization efficiency). Dissolved oxygen is eliminated by either utilizing high catalyst loadings, or lower catalyst loadings combined with a radical initiator. Notably, the methodology is compatible with various solvents (i.e., anisole, 1,2,4-trichlorobenzene (TCB), 1,2-dichlorobenzene (DCB), etc.) and a range of commercially available ligands including tris 2-(dimethylamino)ethylamine (Me₆TREN) and tris(2-pyridylmethyl)amine (TPMA), as well as more inexpensive alternatives such as tris(2-aminoethyl)amine (TREN) and N,N,N‘,N‘‘,N‘‘-pentamethyldiethylenetriamine (PMDETA).