Observing Depolymerization of a RAFT Polymer by Time-Resolved Small-Angle X ray Scattering.

Recently, it has been reported that various polymethacrylates synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization may be depolymerized by heating them to 120 °C in solution. However, insights into the mechanisms and kinetics remain limited. In this work, we monitored the depolymerization process of poly(benzyl methacrylate) in p-xylene using time-resolved small-angle X-ray scattering (SAXS). The results revealed that the weight-average molecular weight gradually decreased, while the z-average radius of gyration remained almost unchanged until approximately half of the repeating units were converted. This unexpected behavior could be well-reproduced by a kinetic model of end-to-end depolymerization (unzipping). This study provides the first direct observation of the structural evolution during depolymerization via an unzipping mechanism.