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G. Peer, M. Mitterbauer, P. Knaack, S. Naumov, M. Markovic, A. Ovsianikov, N. Moszner, R. Liska:
"Tetraacylstannnane as Highly Reactive Type I Photoinitiators for Long Wavelength Curing Applications";
Poster: RadTech USA 2019, Monterey - CA, USA; 15.09.2019 - 18.09.2019.

Photopolymerization induced with visible light receives increased interest in industry as mature applications such as dental composites steadily grow in demand and new applications e.g. lithography-based ceramic manufacturing arise.1 The photoinitiation with long wavelength light is crucial to achieve sufficient curing depths in these filled systems, hence, highly reactive photoinitiators with an absorption range in the visible area are of great significance. Typically, Type II photoinitiators are applicable with visible light but they suffer from lower reactivties due to the bimolecular mechanism for radical formation and often display poor photobleaching behaviour. Type I photoinitiators bypass these issues but mostly initiate the polymerization poorly with light of wavelength above 450 nm.
With the development of tetrakis(2,4,6-trimethylbenzoyl)stannane, a novel photoinitator for long wavelength applications based on acylstannanes is introduced.2,3 Fast photobleaching and high reactivity towards (meth)acrylate double bonds is observed when compared to state of the art Germanium-based Type I photoinitiators.4,5 Moreover, when applying light with a wavelength over 500 nm tetrakis(2,4,6-trimethylbenzoyl)stannane is still able to initate polymerizations in contrast to known acylgermanes. This green light exposure (522 nm LED) enables greaters curing depths in highly filled systems and is therefore immensely beneficial for aforementioned applications. Additionally, unlike many tin organyls, the novel acylstannane and its photoproducts show surprisingly low cytotoxicity.

Photopolymerization, highly reactive photoinitiators, tetrakis(2,4,6-trimethylbenzoyl)stannane, a novel photoinitator