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

Abstract

AbstractFour chalcones with large conjugation structures were designed and synthesized. Strong light absorption within the UV–vis range (λmax = 380–410 nm, εmax = 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.