Studies of Free Radical Polymerization Initiated by Visible Light Photoredox Catalysis

摘要

A visible-light-induced free radical polymerization has been developed. Distinct from living radical polymerizations, this polymerization process is not controlled in the chain growth step but the initiation step, by in situ generation of a constantly low concentration of initiator radicals. On-off experiments demonstrate the ease of controllability of the process, which indicate that it may be an improved method for radical polymerization, since it can be initiated immediately by powering on a light, without any process of preheating the reaction mixture, and can also be sharply stopped by turning off the light, without any cooling process. By adjusting the photo irradiation strength, reaction temperature, and the amount of the initiator system, the molar mass as well as conversion rate can be accurately tuned, which is not easy to realize in other free radical polymerization systems. Notably, a molar mass as high as 5.64 x 10(5) g mol(-1) (D = 1.71) is achieved with this new methodology.