This study explored the abilities of 1‐(9‐anthrylmethyloxy)‐2‐pyridone and related compounds, which absorb long‐wavelength light (>350 nm), to photochemically initiate radical and cationic polymerizations. It was found that the irradiation of the title compounds initiates the radical polymerization of styrene whereas the cationic polymerization of oxetane proceeds in the presence of these photoinitiators to a negligible extent. The behavior of 9‐anthrylmethyloxyl and amidyl radicals in the photopolymerization process of styrene was discussed based on 1H NMR, UV, and fluorescence spectral data. In addition, the photoinitiation ability of the anthrylmethyloxyl end group was also investigated by using its model compound. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2859–2865, 2004

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The irradiation at 340 nm of the title compounds having 9-anthryl and pyren-1-yl groups in methanol was found to give the heterolytic C-O bond cleavage products: 1-hydroxy-2-pyridone and aryl-substituted dimethyl ether (which predominate for the reaction of the former title compound) in addition to 2-pyridone, aryl-substituted methanol and aryl-substituted formaldehyde derived from the homolysis of the N-O bond (which mainly occurs in the photolysis of the latter title compound). It was also found that substitution of the methyl group for hydrogen at the 6-position of the pyridone skeleton in 1-(9-anthrylmethyloxy)-2-pyridone decreases the relative composition of the arylsubstituted dimethyl ether to some extent. These substituent effects on the product compositions were explained in terms of stereoelectronic effects on a charge transfer-type interaction between the aromatic and pyridone rings in the singlet excited state. Analyses of the ground-state conformation for the title compounds by MM2 calculations and 1 H NMR spectroscopy, as well as of their singlet excited-state behaviour, substantiated the existence of a non-emissive intramolecular exciplex intermediate which plays a key role in inducing the C-O bond heterolysis.