Low-Temperature Aqueous RAFT Depolymerization

Abstract The chemical recycling of polymers in aqueous media is a critical yet overlooked challenge in mitigating plastic waste. This research gap severely limits the scope of depolymerization and restricts our fundamental mechanistic understanding. Herein, we report the first aqueous RAFT depolymerization strategy under mild thermal conditions, using poly(poly(ethylene glycol) methacrylate) (PPEGMA) as a model system that is soluble in both aqueous and organic media. Although initially only 39% conversion could be achieved, detailed kinetic profiles revealed a suppressed monomer equilibrium concentration compared to organic media. Interpretation of these findings subsequently enabled higher percentages of regenerated monomer, pushing conversions to >70% at just 90 °C. Notably, the combination of depressed equilibrium thermodynamics and an elevated chain transfer constant (Ctr = 8.2) accelerated the relative rate of degenerative chain transfer by 31-fold, imparting control over depolymerization as demonstrated by uniform molecular weight reduction and the sequential release of monomers from a well-defined block copolymer.