Lower-temperature bulk depolymerization of commercial polymethacrylates

Chemical recycling back to monomer represents an attractive methodology to tackle plastic waste. However, current reports focus on either thermally unstable 'designer' polymers or highly diluted solution depolymerizations. Here we report a simple, yet efficient, bulk main-chain scission pathway, whereby the presence of N-hydroxyphthalimides triggers a hydrogen-atom-transfer reaction on the polymer backbone, followed by the rapid and near-quantitative depolymerization of polymethacrylates. Notably, this strategy can be directly applied to crude commercial polymers, does not rely on preinstalled end-groups or sacrificial co-monomers, operates at relatively low temperatures in the absence of light irradiation and precludes the use of a solvent, therefore enabling direct isolation of pristine monomers in high yields (∼90%). The methodology is compatible with polymethacrylates synthesized by either anionic, free radical or controlled radical polymerization and can also be applied to ultrahigh-molecular-weight materials (>10⁶ Da).