Cationic and Thiol-Ene Photopolymerization upon Red Lights Using Anthraquinone Derivatives as Photoinitiators

Anthraquinone derivatives in combination with an iodonium salt (and optionally N-vinylcarbazole) have been used as photoinitiating systems. One of them (Oil Blue N) that is particularly efficient for cationic, IPN, and thiol-ene polymerization upon red lights (laser diode at 635 nm or household red LED bulb at 630 nm) belongs to the very few systems available at this long wavelength in such experimental conditions (low light intensity in the 10-100 mW/cm(2) range). Their abilities to initiate the cationic photopolymerization of epoxides or vinyl ethers under very soft halogen lamp irradiation have been also investigated. The photochemical mechanisms are studied by steady state photolysis, fluorescence, cyclic voltammetry, and electron spin resonance spin trapping techniques.