Radical generation from photoinitiator (IC 2959) decomposition and radical addition to acrylate. A laser photolysis Fourier transform electron paramagnetic resonance study

Abstract

The decomposition of the photoinitiator 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropan-1-one (trade name IC 2959) was studied using time-resolved laser photolysis Fourier transform electron paramagnetic resonance. The emissive CIDEP polarization of both benzoyl and 2-hydroxy-2-propyl radicals indicates the triplet state of IC 2959 as the radical precursor. By adding n-butyl acrylate it was shown that the addition of 2-hydroxy-2-propyl radicals to the acrylate double bond is two orders of magnitude faster than that of benzoyl radicals.

References

1. K. Dietliker, in Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints, Photoinitiators for Free Radical and Cationic Polymerisation, Vol. 3, ed. P. Oldring, SITA Technology, London, 1991.
2. R. Kirchmayer, G. Bermer, R. Huesler and G. Rist, Farbe Lack, 1980, 88, 910.
3. X. T. P. Phan, Radiat. Curing, 1986, 13, 11.
4. H. Fischer, R. Baer, R. Hany, I. Verhoolen and M. Walbinger, J. Chem. Soc., Perkin Trans. 2, 1990, 787.
5. J.-P. Fouassier and A. Merlin, J. Photochem., 1980, 12, 17.
6. U. Müller and S. Aguirre, J. Prakt. Chem., 1992, 334, 603.
7. C. H. Huggenberger, J. Lipscher and H. Fischer, J. Phys. Chem., 1980, 84, 3467.
8. W. Knolle, U. Müller and R. Mehnert, J. Phys. Chem., submitted.
9. T. Kausche, J. Säuberlich, E. Trobitzsch, D. Beckert and K.-P. Dinse, Chem. Phys., 1996, 208, 375.
10. D. S. Stephenson, Prog. Nucl. Magn. Reson. Spectrosc., 1988, 20, 515.
11. D. Leopold and H. Fischer, J. Chem. Soc., Perkin Trans. 2, 1992, 513.
12. J.-P. Fouassier, D. Ruhlmann, B. Graf, F. Morlet-Savary and F. Wieder, Prog. Org. Coat., 1995, 25, 235.
13. S. N. Batchelor and H. Fischer, J. Phys. Chem., 1996, 100, 9794.