Radical polymerization activity and mechanistic approach in a new three-component photoinitiating system

A new three-component photoinitiating system (based on isopropylthioxanthon e ITX, amine AH, and a bifunctional benzophenone-ketosulfone BP-SK photoini tiator) for acrylate polymerization reactions was investigated through stea dy-state photolysis (photodegradation, redox potentials, and acidity releas e determinations) and time-resolved laser spectroscopy. The photopolymeriza tion activity has been checked. It is shown that addition of ITX to BP-SK/A H clearly enhances the efficiency of the photopolymerization of clear or pi gmented coatings. This is explained (although, a direct interaction between the triplet state of ITX and BP-SK occurs to some extents) on the basis of the interaction of BP-SK with the ketyl radical of ITX. (C) 2000 John Wile y & Sons, Inc.