New highly efficient photoinitiators (PI) based on silyl radicals chemistry are proposed. The ability of these structures to initiate both free radical polymerization and free radical promoted cationic polymerizations is investigated. These compounds (4-tris(trimethylsilyl)silyloxybenzophenone, 2-(1-adamantylcarbonyl)-1,1,1,3,3,3-hexamethyl-2-(trimethylsilyl)trisilane, di(9 H -fluoren-9-yl)(dimethyl)silane, and 4-(bromophenylthio)dimethyl- tert -butylsilane) directly generate silyl radicals under light irradiation as characterized by ESR spin-trapping and laser flash photolysis experiments. High rates of polymerization and high final conversions are obtained. A low oxygen inhibition in the photopolymerization processes is outlined. The present results evidence the high potential of this new class of PI based on the silyl radical chemistry.
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Lalevée et al. (2008) studied this question.