Synthesis and characterization of low-migration bisacylphenylphosphine oxide photoinitiators

Three type I radical photoinitiators (BTPO-1-BTPO-3) containing two acylphosphine oxide structures were designed and synthesized for UV-LED photopolymerization. Three kinds of substituents with different lengths of ethoxy chains were introduced into the molecular structure to form a bisacylphosphine oxide photoinitiator. The effects of different lengths of glycols on the performance of bisacylphosphine oxide photoinitiators were explained by UV-vis absorption spectra, photopolymerization properties, steady-state photolysis, solubility in monomers, and mobility. All of the three new photoinitiators BTPO-1/BTPO-2/BTPO-3 not only possess good solubility in acrylate monomers and excellent photopolymerization properties, but also their mobility in cured films is undetectable by extraction method and UV-Vis spectrum technology. Compared with the mobility of conventional commercial photoinitiator TPO-L (0.98 %), the high molecular weight bisacylphosphine oxides show higher migration stability and environmental friendliness. The results show that the novel bisacylphe-nylphosphine oxide BTPO-1/BTPO-2/BTPO-3 have great potentials as type I free radical photoinitiator for LED light-curing technology in food packaging and biomedical materials fields.