Dimethyl-dihydroacridines as Photocatalysts in the Organocatalyzed Atom Transfer Radical Polymerization of Acrylate Monomers.

Development of photocatalysts (PCs) with diverse properties has been essential in advancement of organocatalyzed atom transfer radical polymerization (O-ATRP). In this work, dimethyl-dihydroacridines are presented as a new family of organic PCs, for the first time enabling controlled polymerization of challenging acrylate monomers via O-ATRP. Structure-property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties and accessing a strongly oxidizing 2PC●+ intermediate for efficient deactivation. In O-ATRP, a combination of PC choice, implementation of continuous-flow reactors, and promotion of deactivation through addition of LiBr are critical to producing well-defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen tolerance of the system and application to diverse acrylate monomers, including the synthesis of well-defined di- and triblock copolymers.