New acyl phosphine oxides as high-performance and low migration type I photoinitiators of radical polymerization

Two low migration acylphosphine oxide photoinitiators (APO and DAPO) containing unsaturated CC double bonds have been designed and synthesized for free radical polymerization. The properties and performances of APO and DAPO in the free radical polymerization of trimethylolpropane triacrylate (TMPTA) were evaluated and compared with the commercial photoinitiator 2,4,6-trimethyl(phenyl) diphenyl oxide (TPO). The results show that DAPO exhibited the best double bond conversion (DC) of TMPTA in the photoinitiators tested under the same reaction conditions. The migration ratio of APO and DAPO was 2/3 and 1/3 of that of TPO respectively indicating lower migration than the conventional photoinitiator, and the solubility of DAPO in monomers was close to that of TPO, which provided the possibility for the industrial application of DAPO.