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

Abstract 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 H 2 O 2 generation, such NIR dye particles photosensitize H 2 O 2 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.