Naphthalimide Derivatives: Substituent Effects on the Photoinitiating Ability in Polymerizations under Near UV, Purple, White and Blue LEDs (385, 395, 405, 455, or 470 nm)

Abstract

Naphthalimide derivatives (NDAs) with amino‐ or alkylthio‐substituents have been synthesized and combined in photoinitiating systems (PIS) with an iodonium salt, N‐vinylcarbazole, an amine, or 2,4,6‐tris(trichloromethyl)‐1,3,5‐triazine to produce radicals, cation radicals, or cations. The photochemical mechanisms are investigated by fluorescence, cyclic voltammetry, laser flash photolysis, electron spin resonance spin trapping, and steady state photolysis techniques. The generated reactive species are capable of initiating the cationic polymerization (CP) of epoxides under air or the free radical polymerization (FRP) of acrylates in laminate upon exposure to visible lights delivered by a halogen lamp, a cold white light‐emitting diode (LED), or LEDs at 385, 395, 405, 455, or 470 nm. Compared to the well‐known camphorquinone based systems, the novel NDA containing PISs exhibit higher efficiencies both for CP and FRP. Remarkably, the photo­bleaching of some NDAs is significant, and colorless final polymer coatings are obtained. The structure/photochemical property relationships of NDAs are discussed in detail (redox potentials, fluorescence, rate constants of reactions, etc.) to shed some light on their respective photoinitiating ability. image