Naphthalic anhydride derivatives: structural effects on their initiating abilities in radical and/or cationic photopolymerizations under visible light

Only one naphthalic anhydride derivative has been reported as light sensitive photoinitiator, this prompted us to further explore the possibility to prepare a new family of photoinitiators based on this scaffold. Therefore, eight naphthalic Naphthalic anhydride derivatives (ANH1-ANH8) have been prepared and combined with an iodonium salt (and optionally N-vinylcarbazole) or an amine (and optionally 2,4,6-tris(trichloromethyl)-1,3,5-triazine) to initiate the cationic polymerization of epoxides and the free radical polymerization of acrylates under different irradiation sources, that is, very soft halogen lamp (μ 12 mW cm^-2), laser diode at 405 nm (μ1.5 mW cm^-2) or blue LED centered at 455 nm (80 mW cm^-2). The ANH6 based photoinitiating systems are particularly efficient for the cationic and the radical photopolymerizations, and even better than that of the well-known camphorquinone based systems. The photochemical mechanisms associated with the chemical structure/photopolymerization efficiency relationships are studied by steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis, and electron spin resonance spin-trapping techniques.