Photoinduced Organocatalyzed Atom Transfer Radical Polymerization Using Low ppm Catalyst Loading

Photoinduced organocatalyzed atom-transfer radical polymerization (O-ATRP) is a controlled radical polymerization methodology that can be mediated by organic photoredox catalysts under the influence of light. However, typical O-ATRP systems require relatively high catalyst loadings (1000 ppm) to achieve control over the polymerization. Here, new core-extended diaryl dihydrophenazine photoredox catalysts were developed for O-ATRP and demonstrated to efficiently operate at low catalyst loadings of 5-50 ppm to produce polymers with excellent molecular weight control and low dispersity, while achieving near-quantitative initiator efficiency. Photophysical and electrochemical properties of the catalysts were computationally predicted and experimentally measured to correlate these properties with improved catalytic performance. Furthermore, these catalysts were utilized to synthesize materials with complex architectures, such as triblock copolymers and star polymers. To demonstrate their broad utility, polymerizations employing these catalysts were successfully scaled up to 5 g and revealed to efficiently operate under air.