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 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.