New chromone based photoinitiators for polymerization reactions under visible light

Novel photoinitiators derived from a chromone structure are proposed for the free radical polymerization of acrylates and the free radical promoted cationic polymerization of epoxides upon exposure to a 457 nm laser diode and even under soft irradiation conditions (blue LED bulb at 462 nm and halogen lamp). Good polymerization profiles are obtained. These original dyes exhibit a push-pull molecular character as revealed by MO calculations. The initiation mechanisms are analyzed through ESR, fluorescence and laser flash photolysis experiments.