Green-Light-Driven PET-RAFT Polymerization Catalyzed by Pyrazino[2,3-f][1,10]phenanthroline Derivatives and Their Mediated Polymerization-Induced Self-Assembly

In recent years, strongly reducing organic photocatalysts (OPCs) featuring arylamine motifs have demonstrated remarkable advantages in reversible-deactivation radical polymerization (RDRP) due to their structural tunability and facile modification. In this study, three donor–acceptor (D-A)-type organic small-molecule photocatalysts based on the pyrazino[2,3- f ][1,10]phenanthroline framework were investigated, each bearing distinct electron-donating substituents. Through systematic screening, DMA-pyzPhen was identified as an optimal catalyst exhibiting broad visible-light absorption, a high molar extinction coefficient (ε max = 21,500), intramolecular charge transfer (ICT) characteristics in the excited state, and superior solubility. Experimental results revealed that this catalyst enables efficient photoinduced electron/energy transfer reversible addition–fragmentation chain transfer (PET-RAFT) polymerization of various monomers under 525 nm irradiation, with an ultralow catalyst loading up to 50 ppb. Notably, DMA-pyzPhen with high fluorescence quantum yield (Φ flour. = 0.17) and excellent solubility enabled controlled fabrication of well-defined fluorescent nanoparticles (spheres, worms, and vesicles) through ethanol-mediated PET-RAFT polymerization-induced self-assembly (PISA) under green light. The as-prepared nanostructures exhibit precisely defined morphologies and bright fluorescence emission, demonstrating significant potential for bioimaging and diagnostic applications.