Design, synthesis, and application of push–pull chalcone-based photoinitiators for free radical polymerization†

The development of effective photoinitiators for LED polymerization is still an emerging challenge. Two pull–push conjugate chalcone derivatives were designed and synthesized as the photonitiators for free radical polymerization. (E)-2-(Benzo[d]thiazol-2-yl)-3-(4-((E)-3-(4-(dimethylamino)phenyl)-3-oxoprop-1-en-1-yl)phenyl)acrylonitrile (DMAP-CN) and (E)-3-(4-bromophenyl)-1-(4-(dimethylamino)phenyl)prop-2-en-1-one (BDMAP) were synthesized and used as photoinitiators. The photopolymerization kinetics results demonstrated that DMAP-CN and BDMAP could initiate polymerization of HDDA in both one-component and two-component photoinitiating systems. But DMAP-CN exhibited less reactivity than the BDMAP systems on free radical polymerization. To explain the photoinitiating mechanisms, we used different complementary techniques including real-time Fourier transform infrared spectroscopy, UV-visible absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry, electron paramagnetic resonance spin trapping (EPR-ST) experiments and molecular modelling calculations.