Terthiophene Derivative-Based Photoinitiating Systems for Free Radical and Cationic Polymerization under Blue LEDs

Terthiophene derivatives were prepared and utilized as photoinitiators of photopolymerization reactions upon exposure to LEDs (410 and 445 nm). The photochemical mechanisms of the terthiophene-based photoinitiating systems were investigated and confirmed by steady-state photolysis, fluorescence quenching, and electron paramagnetic resonance spin-trapping techniques. The photoinitiation ability of terthiophene derivatives in combination with the iodonium salt and optionally with a tertiary amine in the free radical polymerization of multifunctional acrylates and cationic polymerization of epoxides under mild light irradiation was investigated. Exceptionally, a sodium salt form of a terthiophene derivative presented exceeding water solubility and admirable efficiency in rapid hydrogel formation from the 2-hydroxy ethyl acrylate and water blend. The storage stability of the effective photoinitiating systems in the formulations was also studied under moderate conditions.