Hydrophobic NIR Photocatalysts for High‐Throughput RAFT Aqueous Solution Polymerization: Achieving Ultrahigh Molecular Weights with 4‐ppm Dye Colloids

Near-infrared (NIR) photocontrolled radical polymerization offers the opportunity to combine NIR's deep-tissue penetration and biocompatibility with the precision and versatility afforded by controlled polymerization. However, its development is hindered by the scarcity of water-soluble NIR photocatalysts. Moreover, examples of systems achieving high molecular weights remain limited. To overcome these limitations, we have prepared colloidal NIR photocatalysts to conduct efficient reversible addition-fragmentation chain transfer (RAFT) polymerization in aqueous media. Combined with glucose oxidase for in situ degassing and H₂O₂ generation, such NIR dye particles photosensitize H₂O₂ to produce a controlled flux of hydroxyl radicals. This novel enzyme-NIR strategy enables high-throughput RAFT aqueous solution polymerization of various vinyl monomers with excellent control. Notably, ultrahigh molecular weight (M_n > 1,000 kg mol^-1) homopolymers can be obtained for polymerizations conducted through an opaque biological barrier at ultralow photocatalyst loadings (4 ppm). Thus, such enzyme-NIR formulations enable precision polymer syntheses even in physiologically relevant environments.