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M. Mitterbauer, M. Haas, H. Stüger, N. Moszner, R. Liska:
"Visible light photoinitiators based on silicon for the curing of dental formulations";
Poster: 4th European Symposium of Photopolymer Science, Leipzig; 11.09.2016 - 14.09.2016; in: "ESPS 2016", (2016), S. P-14.

The curing of dental filling materials is one example of a large number of modern applications (e.g. lithography- based ceramic manufacturing [1]) for visible light photopolymerization. Currently, a bimolecular photoinitiating system based on camphorquinone / ethyl p-(dimethylamino)-benzoate (CQ/DMAB) is applied within this field, but shows quite limited reactivity. In the case of other more efficient cleavable photoinitiators like bisacylphosphine oxides, the absorption band of these compounds does not overlap properly with the emission band of the currently applied dental blue LEDs. Acylgermane-based structures also reveal drawbacks like their very expensive synthesis. Since photoinitators based on silicon might show similar absorption properties as their germanium analogues, the synthesis and photochemical characterization of such compounds were the target of this study. Improved reactivity should be achieved by repressing the photoinduced formation of a siloxycarbene, also known as Brook-rearrangement. The strategy of multiple substitution at the silicon atom with mesitoyl groups led to a successful synthesis of tetrakis(mesitoyl)silane, which revealed good reactivity in photopolymerization of acrylates. Furthermore, the overlap of the nπ* absorption band of tetrakis(mesitoyl)silane with the emission band of dental LEDs was quite satisfying compared to the bisacylphosphine oxides. However, suitable strategies for the stabilization in aqueous media need to be established.