Thiyl Radical Generation in Thiol or Disulfide Containing Photosensitive Systems

The generation of thiyl radicals in various multicomponent photosensitive systems based on a ketone, a coumarin or a ketocoumarin and containing a thiol or a disulfide and eventually chloro bis‐imidazole has been studied through laser flash photolysis. A set of more than 70 new interaction rate constants is provided. The measurements of the quantum yields in sulfur radicals and the rate constants of the different processes in many combinations as well as the molecular orbital calculations allow to discuss the driving factors of the involved reactions. This approach should shed some light on the possible explanations of the high performance of some of these combinations when used as photoinitiating systems for radical photopolymerization reactions. magnified image