Photoinitiation Mechanism and Ability of Monoamino-Substituted Anthraquinone Derivatives as Cationic Photoinitiators of Polymerization under LEDs

The design and development of photoinitiating systems applicable to UV or even visible light delivered from light-emitting diodes (LEDs) has been attracting increasing attention due to their great potential applications in various fields. Compared to the strategy of synthesizing novel compounds, the exploration of existing chemicals with interesting photochemical/photophysical properties for their usage as photoinitiators is more appealing and easily commercialized. Nevertheless, a number of compounds such as monoamino-substituted anthraquinone derivatives, which are intensively investigated for their photophysical and photochemical properties, have seldom been studied for their roles as photoinitiators under LED irradiation. Herein, three monoamino-substituted anthraquinone derivatives, that is, 1-aminoanthraquinone, 1-(methylamino)anthraquinone and 1-(benzamido)anthraquinone, are studied for their potential as photoinitiators. The photoinitiation mechanism of these monoamino-substituted anthraquinone derivatives, when combined with iodonium salt, is first clarified using computational quantum chemistry, fluorescence, steady-state photolysis, and electron spin resonance spin-trapping techniques. Then, their photoinitiation ability for the cationic photopolymerization of epoxide and divinyl ether monomers is also investigated.