Carbon dots as green photocatalysts for atom transfer radical polymerization of methacrylates

We herein report the use of carbon dots (CDs) in photoinduced atom transfer radical polymerizations (ATRP) as green metal-free sensitizers. In particular, the production of a polymethacrylate (poly-METAC, METAC = 2-(methacryloyloxy)ethyl]trimethylammonium chloride) by using cheap and easily affordable CDs made from citric acid and diethylenetriamine, under both ultraviolet (UV, lambda = 365 nm) and visible light was studied. Different solvent systems have been tested and a CuII complex was used as catalyst. Under the best conditions a polymer in 89% conversion and with a narrow dispersity (1.4) was obtained. The first order kinetics and the "on-off" experiments gave further evidence of the constant concentration of radicals and of the controlled mechanism of the polymerization.