Novel chalcone derivatives with large conjugation structures as photosensitizers for versatile photopolymerization

Four chalcones with large conjugation structures were designed and synthesized. Strong light absorption within the UV–vis range (λ_max = 380–410 nm, ε_max = 10,200–33,600 M^?1 cm^?1) matched the emission of light-emitting diodes within 385–450 nm. Compared with that of phenyl ring-containing chalcone, the bathochromic shift of the four chalcones was due to the enlarged conjugation structure and the intramolecular charge transfer effect. The reactive species produced from two- or three-component photoinitiating systems (PISs) based on chalcone-containing triphenyl amine and N-ethyl carbazole combined with an iodonium salt or/and an amine were highly efficient for versatile photopolymerizations (i.e., radical, cationic, blending, and thiol-ene polymerizations) upon soft exposure conditions (385–425 nm LEDs). UV–vis spectra, theoretical calculation, electrochemistry, real-time nuclear magnetic resonance spectra, and fluorescence quenching were investigated to determine the photochemical mechanism. Chalcone photoisomerization, which mainly occurred in anthracene-containing chalcone, weakened the initiation ability of the PISs. These chalcones have promising applications in photopolymerization.