Zirconium Complexes to Overcome Oxygen Inhibition in Free-Radical Photopolymerization of Acrylates: Kinetic, Mechanism, and Depth Profiling

The photopolymerization process of acrylate coatings initiated by visible light (lambda > 380 nm) and performed in air was studied in the presence of zirconium complexes. Depth profiling experiments were performed using confocal Raman microscopy showing that the conversion, which is low at the surface of the sample, increases with increasing depth and reaches a full conversion close to the substrate. RT-FTIR spectroscopy corroborates Raman results in evidencing the efficiency of some zirconium compounds to reduce oxygen inhibition. Finally, laser flash photolysis experiments revealed that the beneficial effect in air is attributable to the reaction of the zirconium complex on the peroxyl radicals formed from the reaction of oxygen with radicals. Therefore, the oxygen present in the medium is depleted, allowing a better efficiency of the photopolymerization process. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 5169-5175, 2011