Two UV-LED Excited One-component Thioxanthone-based Photoinitiators with High performance, Low migration

Developing high performance UV-LED excited photoinitiators is one of research focuses in the field of photopolymerization. Thioxanthone derivatives, which reveal outstanding absorptions in the UV-Vis spectra, have potential excited by UV light source. In this article, two novel thioxanthone-based photoinitiators, 9-oxo-9H-thioxanthen-2-yl 4-(dimethylamino)benzoate (TXOH-DB) and 1-chloro-9-oxo-9H-thioxanthen-4-yl 4-(dimethylamino)benzoate (TXCl-DB), were designed and synthesized, and their structure has been confirmed by FT-IR and 1H NMR. The UV-vis spectra showed that these two photoinitiators appeared redshift compare with TX, and the UV absorption ability of TXCl-DB was stronger than TX. Steady state photolysis experiments and photopolymerization experiments indicated that TXOH-DB and TXCl-DB were one-component photoinitiators and could successfully initiate 2-hydroxyethyl acrylate (HEA), 1,6-hexanediol diacrylate (HDDA) and Trimethylolpropane triacrylate (TMPTA) under UV-LED @395 nm (10 W) without the presence of co-initiatar. In addition, TXOH-DB and TXCl-DB have better migration stability and have the potential for use in UV curing systems, especially in food packaging and biomedical applications.