Iodine-mediated photoATRP in aqueous media with oxygen tolerance

Abstract

Water is an environmentally friendly medium for conducting reversible deactivation radical polymerizations. In this paper, we report the investigation of iodine-mediated photocontrolled atom transfer radical polymerization (photoATRP) in aqueous media. The iodine-based initiator was generated by an in situ halogen exchange from a commercially available bromine-based initiator, ethyl α-bromophenylacetate, using different iodide salts. Fast and well-controlled polymerization of a water-soluble methacrylate monomer was achieved in water under visible light irradiation, including blue, green and yellow lights. The nature of the reaction medium greatly affected the kinetics and control over the growth of polymers. Polymerizations in water resulted in a well-controlled reaction that provided high monomer conversion and polymers with low dispersities, whereas control over the polymerization was poor in bulk or in an organic solvent, N,N-dimethylformamide. Polymerizations were performed over a wide range of visible light in the absence of any photocatalyst. The selection of water as a reaction medium enabled use of iodide salts without the need for solubilizing agents. Moreover, iodine-mediated photoATRP was successfully performed in the presence of residual oxygen, signifying the potential of this polymerization system to tolerate oxygen without performing deoxygenation processes.