Supramolecular near‐infrared photocatalysts for efficient and oxygen‐tolerant aqueous RAFT polymerization

Near-infrared (NIR) photocontrolled polymerization in aqueous media is promising for bioapplications. However, it typically suffers from low polymerization efficiency and requires high catalyst loadings due to the aggregated nature of the photocatalyst. Herein, we report a supramolecular strategy to overcome this limitation via host–guest complexation between an anionic photocatalyst and a cationic macrocycle. Spectroscopic and computational studies confirmed the formation of stable 1:1 host–guest complexes via synergistic electrostatic, π-π, and hydrophobic interactions. Supramolecular complexation effectively suppresses photocatalyst aggregation and significantly enhances oxygen tolerance and reaction kinetics, enabling high-throughput, open-to-air NIR-mediated reversible addition-fragmentation chain-transfer (RAFT) polymerizations to be conducted in aqueous media with excellent control over molecular weight and dispersity. High conversions and low dispersities were achieved even for polymerizations conducted through thick porcine tissue barriers, demonstrating excellent NIR penetration depth. This work provides a versatile supramolecular approach to enhancing photocatalyst performance, highlighting new avenues for precision polymer synthesis under biologically relevant conditions.