Synthesis and properties of novel bis-chalcone-based photoinitiators for LED polymerization with photobleaching and low migration

In this work, six bis-chalcone-based photoinitiators (1E,4E)-1,5-diphenylpenta-1,4-dien-3-one (DKE-1), (1E,4E)-1,5-di(naphthalen-2-yl) penta-1,4-dien-3-one (DKE-2), (1E,4E)-1,5-di(anthracen-9-yl)penta-1,4-dien-3-one (DKE-3), (1E,4E)-1,5-di(pyren-1-yl)penta-1,4-dien-3-one (DKE-4), (1E,3E,6E,8E)-1,9-diphenylnona-1,3,6,8-tetraen-5-one (DKE-5) and (3E,6E)-1,9-diphenylnona-3,6-dien-1,8-diyn-5-one (DKE-6) were synthesized by Claisen-Schmidt reaction. The influence of different polycyclic aromatic hydrocarbon structures and unsaturated groups on the maximum absorption wavelength, solubility and migration properties of DKEs was studied. It was found that with the increase of the number of benzene rings for DKE-1 to DKE-4 and the introduction of CC, CC bonds for DKE-5-DKE-6 in the molecular structure, the absorption wavelength gradually red-shifted to the visible region, the maximum absorption wavelength of DKE-4 and DKE-6 was 442 nm, 395 nm respectively. Besides, DKE-5 and DKE-6 can effectively solve the problem of poor solubility. Three-component photoinitiating system of DKEs/iodonium/amine presented efficiently photopolymerization and the double bond conversion can reach >80 %. DKEs have shown certain photobleaching properties, indicating that it can be used for deep curing of coatings. In addition, DKEs have low migration, the migration ratio of DKE-4 was low to 0.7 %.