Investigation of Photoinitiator Reactivity: the Cleavage Process

A deep investigation of the photochemical and chemical reactivity of photoinitiating systems (PIS) of polymerisation reactions is presented. Time resolved absorption spectroscopy in the picosecond time scale and laser induced photoacoustic spectroscopy were used to obtain data on the kinetics and the thermodynamics of the cleavage process of 2-hydroxy-2-methyl-1-phenyl-1-propanone. Molecular modeling calculations performed at high level of theory are shown to provide a clear picture on the processes that govern the overall efficiency of PIS and more particularly on the cleavage process. The effect of changing the phenyl moiety for a heterocycle is also discussed.