Synthesis and application of new S -benzoheterocycle thiobenzoates photoinitiators

A series of free radical photoinitiators with thioester bonds were synthesized by the nucleophilic substitution reaction of acyl chloride and thiol or thiophenol. These compounds could be efficiently obtained under mild reaction conditions and were fully characterized by 1 H NMR, 13 C NMR and high-resolution mass spectrometry. This kind of compounds exhibited a strong ultraviolet–visible light absorption spectrum with an extended absorption around 330 nm in DMSO. Moreover, these compounds were utilized as free radical photoinitiators in ultraviolet curing and the resulting films exhibited comparable mechanical properties in comparison with commercially available photoinitiators, such as 1-hydroxycyclohexyl phenyl ketone (Irgacure 184) and benzophenone. We also proposed a probable photoinitiated polymerization mechanism for S -benzoheterocycle thiobenzoates as photoinitiators.