Depolymerization of Polymethacrylates by Iron ATRP

Recycling of polymers has become increasingly relevant with the focus on a circular economy. Controlled radical polymerizations create an avenue for polymerization and depolymerization through activation of the dormant polymer chain-end functionality. Here, the depolymerizations of poly(methyl methacrylate) (PMMA) and poly(n-butyl methacrylate) (PBMA) macroinitiators with terminal chlorine chain-end functionality mediated by iron chloride salts and iron powder at 170 °C are reported. The depolymerizations were conducted with polystyrene as internal standard for kinetics measurements by GPC. Higher conversion and depolymerization rates were achieved in tetra(ethylene glycol) dimethyl ether than in 1,2,4-trichlorobenzene. Depolymerization with zerovalent Fe0 as a supplemental activator and reducing agent was the most effective, reaching >70% conversion at 10 wt % solid polymethacrylate loadings with fast reaction rates. The monomer isolated during the depolymerization was recovered through distillation.