Photochemistry of Quaternary Ammonium Thiocyanates and Their Behavior as Photobase Generators

Photochemical reactions of quaternary ammonium salts (QASs) bearing phenacyl groups and
thiocyanate anions were investigated, and their performance as a catalyst for curing of epoxides was demonstrated. Upon UV-irradiation, QASs having thiocyanate anions generated amines, which
induced a transformation of resulting thioisocyanates into oxazole-2-thiones, and finally the amines and oxazole-2-thiones made amine-thiolate complexes. Using model compounds, the mixture of a thiol and an amine was confirmed to be effective for lowering crosslinking temperature of polymers or oligomers bearing epoxy groups. Poly(glycidyl methacrylate) films were found to become insoluble in the presence of QASs having thiocyanates on UV-irradiation followed by thermal treatment.