Complex triarylsulfonium salt photoinitiators. I. The identification,characterization, and syntheses of a new class of triarylsulfonium salt photoinitiators

Dilphenyl-4-thiophenoxyphenylsulfonium salts have been found to be more efficient cationic photoinitiators than the highly photoactive triphenylsulfonium salts. The former compounds were identified as by-products produced in the preparation of triphenylsulfonium chloride from benzene, chlorine, sulfur monochloride, and aluminum chloride. Confirmation of the structure was made by NMR and UV spectroscopy as well as by independent synthesis. The photoinitiated cationic polymerization of cyclohexene oxide and other epoxy monomers was carried out to demonstrate the higher efficiency of diphenyl-4-thiophenoxysulfonium hexafluoroarsenate as compared to the corresponding triphenylsulfonium salt.