Chalcone derivatives as highly versatile photoinitiators for radical, cationic, thiol-ene and IPN polymerization reactions upon exposure to visible light

Chalcone derivatives are proposed as novel photoinitiators for polymerization upon exposure to visible light (even under soft irradiation conditions: blue LED bulb at 462 nm, halogen lamp, and sunlight). Remarkably, these structures are highly versatile allowing access to photoinitiating systems for (i) the free radical polymerization of acrylates, (ii) the cationic polymerization of epoxides and vinyl ethers, (iii) the synthesis of interpenetrated polymer networks (IPNs) and (iv) the thiol-ene processes. Excellent polymerization profiles are obtained. The initiation mechanisms are analyzed through ESR, steady state photolysis, cyclic voltammetry, laser flash photolysis and fluorescence experiments.