Visible Light and Sunlight Photoinduced ATRP with ppm of Cu Catalyst

Photochemically induced ATRP was performed with visible light and sunlight in the presence of parts per million (ppm) copper catalysts. Illumination of the reaction mixture yielded polymerization in case of 392 and 450 nm light but not for 631 nm light. Sunlight was also a viable source for the photoinduced ATRP. Control experiments suggest photoreduction of the Cu^II complex (ligand to metal charge transfer in the excited state), yielding a Cu^I complex, and a bromine radical that can initiate polymerization. No photoactivation of Cu^I complex was detected. This implies that the mechanism of ATRP in the presence of light is a hybrid of ICAR and ARGET ATRP. The method was also used to synthesize block copolymers and polymerizations in water.