Double benzylidene ketones as photoinitiators for visible light photopolymerization

In this work, four novel double benzylidene ketone dyes (TPA-H, CZ-H, TPA-C, and CZ-C) with D-A structure were synthesized and showed good charge transfer characteristics and high absorption capability in the visible light range. The double benzylidene ketone dyes can be used as type II photoinitiators to initiate free radical photopolymerization (FRP) or as charge transfer sensitizers to sensitize diaryliodonium salt (ONI) synergistically for the initiation of FRP and cationic photopolymerization (CP) together with aromatic amine groups under 460 and 532 nm LED light sources. FRP and CP experiments revealed that TPA-C and CZ-C with polyarylamine groups had high sensitization and initiation activities under 460 and 532 nm LED light sources. The photochemical properties of the initiator system were investigated by means of steady-state photolysis, fluorescence quenching, cyclic voltammetry, and electron spin resonance spin trapping experiments.