Efficient visible photoinitiator containing linked dye-coinitiator and iodonium salt for free radical polymerization

Dye-linked initiators consisting of erythrosine B as a chromophore and ethyl 4-dimethylaminobenzoate as an electron donor linked by a different number of methylene units were prepared to achieve efficient photoinitiators of free radical polymerization in a visible-light region. The relative photoinitiating efficiencies of novel photoinitiators in photopolymerization of acrylates were evaluated. The results showed that the photoinitiating system composed of the dye-linked dyad with short methylene unit chain and diphenyliodonium salt exhibited a remarkable increase in the photoinitiation ability compared to unlinked three-component system. The enhancement mechanism aroused by the onium salt was investigated. These results showed that the excellent initiating efficiency of this system could be attributed to the favorable intramolecular photoinduced electron transfer and the close distance between reaction components caused by electrostatic interactions. This result demonstrated the importance and potential of the linked photoinitiator in the design of new efficient photoinitiators.