New functionalized aromatic ketones as photoinitiating systems for near visible and visible light induced polymerizations

Novel functionalized ketones (K_PY) incorporating one/two pyrene moieties or a pyridinium chromophore for radical and/or cationic polymerization under soft irradiation conditions (Xe–Hg lamp, halogen lamp) are proposed. These compounds exhibit red-shifted absorptions and enhanced molar extinction coefficients (e.g. for near visible lights (395 nm), the absorption can be increased by a factor of 20). The ability of the various K_PY/amine couple in the radical polymerization of an acrylate (up to 75% conversion) and the different K_PY/diphenyliodonium salt system in the cationic polymerization of an epoxide (up to 70% conversion) is often better than that of reference compounds. These structures are also very efficient to overcome the oxygen inhibition. Molecular orbital calculations, ESR experiments and laser flash photolysis allow an investigation of the absorption properties, the excited state processes and the involved initiation mechanisms.