New role of aminothiazonaphthalimide derivatives: outstanding photoinitiators for cationic and radical photopolymerizations under visible LEDs

Aminothiazonaphthalimide derivatives (ATNDs) can act as photoinitiators (when combined with iodonium salt, amine, 2,4,6-tris(trichloromethyl)-1,3,5-triazine or N-vinylcarbazole) to start the ring-opening cationic polymerization of epoxides or the radical polymerization of acrylates upon exposure to visible LEDs (405 nm or 455 nm) or a polychromatic visible light delivered by a halogen lamp. The photoinitiating ability of some of these systems is even better than that of the well-known camphorquinone based systems and the commercial bisacylphosphine oxide type I photoinitiator, unambiguously showing their outstanding performance. The structure/reactivity relationships as well as the particular role played by the position of the aminothiazo-substituent in the ATNDs is revealed by mechanistic studies using steady state photolysis, cyclic voltammetry, fluorescence, laser flash photolysis, and electron spin resonance spin trapping techniques.