Investigation of Processes in Photoinitiating Systems through ESR Spin Trapping and Kinetic ESR

In Free Radical Photopolymerization (FRP), the role of the photoinitiator (PI) is very important towards the overall polymerization efficiency.[1-4] A lot of studies have already been devoted to the PI reactivity. The PI cleavage processes have been mainly investigated through various time resolved laser spectroscopy technique, e.g. laser flash photolysis (LFP), CIDNP, CIDEP, Continuous Wave Electron Spin Resonance CW-ESR and Time Resolved Electron Spin Resonance TR-ESR techniques [5,6-7]. The ESR Spin Trapping technique (ESR-ST), recognized as particularly powerful for the identification of radicals, [8-10] is highly valuable for short lived radicals hardly accessible by CW-ESR or TR-ESR. Despite a widespread use in life sciences, [9] very few studies by ESR-ST have been devoted to photoinitiators.