Initiators for Continuous Activator Regeneration (ICAR) Depolymerization

Chemical recycling of polymers synthesized by atom transfer radical polymerization (ATRP) typically requires high temperatures (i.e., 170 °C) to operate effectively, not only consuming unnecessary energy but also compromising depolymerization yields due to unavoidable end-group deterioration. To overcome this, the concept of initiators for continuous activator regeneration (ICAR) depolymerization is introduced herein as a broadly applicable approach to significantly reduce reaction temperatures for ATRP depolymerizations. Addition of commercially available free radical initiators enables the on-demand increase of depolymerization efficiency from <1% to 96%, achieving monomer generation at 120 °C, with conversions on par with thermal reversible addition-fragmentation chain transfer (RAFT) depolymerizations. Incubation studies confirm the elimination of deleterious side reactions at the milder temperatures employed, while the methodology can be scaled up to 1 g. The robustness and versatility of ICAR depolymerization is further demonstrated by the possibility to effectively depolymerize both chlorine and bromine terminated polymers and its compatibility with both copper and iron catalysts.