Highly Efficient Near-Infrared Photoinduced Electron/Energy Transfer-Reversible Addition–Fragmentation Chain Transfer Polymerization via the Energy Transfer Upconversion Mechanism

Near-infrared (NIR) light-mediated polymerization has been of particular interest owing to the deep penetration into opaque materials, giving rise to great potential for biomedical applications and solar photochemistry. Photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization presented unprecedented spatiotemporal control over the controlled radical polymerization process. Herein, we greatly extended the NIR region up to 980 nm by introducing rationally designed upconversion nanocrystals with low toxicity and resistance to photobleaching into PET-RAFT polymerization. Well-defined polymers with predictable molecular weight and narrow dispersity were prepared within a few hours by 980 nm NIR light-regulated PET-RAFT polymerization via the energy transfer upconversion mechanism. The livingness feature of this photopolymerization was confirmed by polymerization kinetics, chain extension experiments, and multiple controlled "on–off" light switching cycles. Furthermore, the polymerizations could be successfully performed using different monomers, in the presence of several visible light-proof barriers (i.e., pork/chicken skin) and even under aerobic conditions, demonstrating the multifold advantages of our approach.