Near-infrared-driven photothermal atom transfer radical polymerization

Reversible-deactivation radical polymerization (RDRP) is a powerful tool in modern polymer chemistry, enabling the synthesis of well-defined materials with complex architectures. Among RDRP methods, photoinduced atom transfer radical polymerization (photo-ATRP) and photoinduced reversible addition-fragmentation chain transfer (photo-RAFT) polymerization are two of the most common approaches. However, in the context of biological applications, their use is often hampered by their reliance on UV light and their sensitivity to oxygen. Herein, we present a photothermal approach utilizing gold nanobipyramids (NBPs) to drive both ATRP and RAFT polymerizations in aqueous media under aerobic conditions. By precisely tuning the morphology of NBPs, we harnessed their ability to generate localized heating upon near-infrared (NIR) light irradiation (780 nm). This localized heating efficiently triggered radical generation from a water-soluble azo initiator (2,2'-azobis(2-amidinopropane)dihydrochloride, AAPH). The resulting radical flux enabled well-controlled ATRP of oligo(ethylene oxide) methyl ether methacrylate (OEOMA₅₀₀) at low volume (250 µL) in a 96-well plate open to air. The photothermal ATRP exhibited excellent temporal control, enabling rapid on/off switching of polymerization simply by NIR light modulation. The versatility of our methodology was further demonstrated by its successful application in photo-RAFT polymerization, achieving controlled polymerization of various monomer classes under aqueous conditions. This robust, nanotechnology-enabled photothermal approach opens new avenues for advanced materials synthesis and high-throughput applications by overcoming key limitations of traditional photo-RDRP systems.