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 bisacylphenylphosphine 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.