Controlled radical depolymerization: Structural differentiation and molecular weight control

Depolymerization of polymers synthesized by reversible deactivation radical polymerization (RDRP) has recently emerged as a promising chemical recycling method for a circular economy. However, current depolymerization reactions are typically uncontrolled (i.e., molecular weight remains unchanged), thus providing no handle over the molecular weight and limiting further applications. Herein, we report a controlled reversible addition-fragmentation chain-transfer (RAFT) depolymerization that enables a gradual decrease in molecular weight, resembling the reverse process of controlled polymerization. The key to our strategy is to enhance chain deactivation over depropagation by employing RAFT agents with high chain-transfer activity, resulting in the gradual unzipping of polymer chains and a linear decrease in molecular weight over time. As an exemplary application, we demonstrate that controlled depolymerization enables the structural characterization of various copolymers (i.e., AB diblock versus BA diblock versus statistical versus gradient) by facilitating the sequential release of monomers from the chain end, pushing the boundaries of depolymerization and unlocking new applications.