Atom Transfer Radical Polymerization Driven by Near-Infrared Light with Recyclable Upconversion Nanoparticles

Near-infrared (NIR) photoinduced chemical processes are highly attractive for specific applications owing to the deep penetration of NIR into the nontransparent materials including biological and synthetic materials. Robust NIR photoinduced atom transfer radical polymerization (photoATRP) was achieved using upconversion nanoparticles (UCNPs) as an internal light converter to turn a 980 nm NIR light to the wavelength of UV/vislight. This NIR photoATRP was capable of polymerizing both hydrophobic and hydrophilic monomers at a low loading of ppm concentrations of the CuBr2/tris(2-pyridylmethyl)amine catalyst under the irradiation of a 980 nm NIR light (4 W/cm2) and UCNPs with reusable performance, providing well-defined polymers with predetermined molecular weight, low dispersity, and excellent chain-end fidelity. The switching of light “on/off” showed an excellent temporal control of the polymerization. The NIR photoATRP exhibited excellent penetrations through several visible light-proof barriers using NIR light, and it may provide future directions of photopolymerization in nontransparent systems, especially biological systems containing photosensitive moieties.