Enone dyes as visible photoinitiator in radical polymerization: The influence of peripheral N-alkylated (hetero)aromatic amine group

Abstract In this work, three enone dyes (C3s) bearing N-alkylated pyrrole (C3PY), indole (C3ID) and carbazole (C3CZ) group were synthesized and characterized to explore the effect of peripheral group on their photoinitiation ability. C3s display good light absorption in the region of 300–500 nm. Under 405/460 nm LED irradiation, the polymerization kinetics of a diacrylate monomer in the presence of one-component C3s or bimolecular C3s/triethanolamine (TEOA) were investigated by Real-time FT-IR technology. Polymerization profiles show that C3s could initiate the polymerization and TEOA significantly promote the initiation efficiency of C3CZ, while this acceleration effect is relatively small for C3PY and C3ID. To decipher these phenomenon, steady state photolysis, cyclic voltammetry and theoretical calculation were jointly performed. Accordingly, it is proposed that C3PY and C3ID tend to photolyze through intramolecular hydrogen abstraction. This work show that the peripheral group strongly affect the initiation ability of enone photoinitiator.