Reversing RAFT Polymerization: Near-Quantitative Monomer Generation Via a Catalyst-Free Depolymerization Approach

Abstract

The ability to reverse controlled radical polymerization and regenerate the monomer would be highly beneficial for both fundamental research and applications, yet this has remained very challenging to achieve. Herein, we report a near-quantitative (up to 92%) and catalyst-free depolymerization of various linear, bulky, cross-linked, and functional polymethacrylates made by reversible addition–fragmentation chain-transfer (RAFT) polymerization. Key to our approach is to exploit the high end-group fidelity of RAFT polymers to generate chain-end radicals at 120 °C. These radicals trigger a rapid unzipping of both conventional (e.g., poly­(methyl methacrylate)) and bulky (e.g., poly­(oligo­(ethylene glycol) methyl ether methacrylate)) polymers. Importantly, the depolymerization product can be utilized to either reconstruct the linear polymer or create an entirely new insoluble gel that can also be subjected to depolymerization. This work expands the potential of polymers made by controlled radical polymerization, pushes the boundaries of depolymerization, offers intriguing mechanistic aspects, and enables new applications.

Synthesis and Phase Behavior of a Platform of CO2-Soluble Functional Gradient Copolymers Bearing Metal-Complexing Units

“…Indeed, the cleavage of the dithio group in the case of unreacted CTA (R-S-C(S)Z, in this work, R = EtOC(O)CH(CH 3 )-and Z = Ph) occurs close to 200 • C, depending on the R group of the CTA. The higher residual mass by TGA after removing the end-group coming from the RAFT agent is also consistent with some works showing the lower thermal stability of RAFT polymers, even sometimes opening the route to a free depolymerization approach [84,85]. On the other hand, it is important to mention that the stability of the R group is increased by the integration of the CTA inside the polymer chain [81,86,87].…”

Rational design of a multi-in-one heterofunctional agent for versatile topological transformation of multisite multisegmented polystyrenes

“…This unusual phenomenon could be ascribed to the partial depolymerization of PSt at 150 °C, which was more or less similar to the catalyst-free depolymerization of RAFT-synthesized polymethacrylates at 120 °C. 80 To avoid the efficient depolymerization of PSt, F4 was chosen to investigate the thermolysis kinetics at a low concentration. As the DMF solution of F4 (c p = 16 mg mL −1 ) was heated at 150 °C for 48 h, the evolution of GPC traces with increasing time was carefully monitored.…”

Promoting Halogen-Bonding Catalyzed Living Radical Polymerization through Ion-Pair Strain

“…[46][47][48][49] Cleaving the end-groups of the polymers to generate radicals and increasing the reaction temperature above the ceiling temperature of polymerization are the two prerequisites to reversing the radical polymerization. [50][51][52] Because TACP-I shows high catalytic efficiency in radicalgeneration reactions, we wondered that if it can also be applied in catalyzing the depolymerization reaction. To this end, premade PMMA-I was used as a test polymer for the depolymerization reaction.…”