Photochemistry and Polymerization Efficiency of Bis-imidazole based Photoinitiator Systems

Photopolymerization efficiency of an acrylate formulation (Ebecryl 605) under light irradiation at 365 nm has been evaluated by using RTFTIR. The role of various multicomponent photoinitiating systems based on bis imidazole derivatives, in the presence or not of an aminobenzophenone, N-phenylglycine and several iodonium salt derivatives has been emphasized. Excited state processes in these two-, three- or four- component systems have been investigated through time resolved laser spectroscopy. The different photophysical processes and photochemical reactions involved are defined and the role of each partner is discussed : this helps to explain the high performance of the three- and four- component photoinitiating systems.