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J. Steindl, T. Koch, N. Moszner, C. Gorsche:
"Silane-Ene-Chemistry: An approach towards regulated photopolymer networks";
Poster: 4th European Symposium of Photopolymer Science, Leipzig; 2016-09-11 - 2016-09-14; in: "ESPS 2016", (2016), P-33.

Photopolymers are a widely spread and important class of materials. Thereby, the evolution of high shrinkage stress during the reaction and very brittle behaviour of the resulting polymers are still unsolved problems. These drawbacks can be attributed to the very inhomogeneous network structure of the radically cured crosslinking resins [1]. Therefore, a strong demand for additives, which act as network regulators, arises.
A widespread approach is the use of chain transfer agents (CTAs) for the radical polymerisation, which lead to more homogenous networks, hence better thermo-mechanical properties. The most popular CTAs are thiols (thiol-ene-chemistry) [2], but good results are also received with addition fragmentation chain transfer (AFCT) reagents [3] (e.g. β-allyl sulfones [4] or vinyl sulfonate esters [5].
Furthermore, Lalevée et al. [6] suggested silanes as alternative CTAs (Scheme 1).


Scheme 1: Mechanism of the silane-ene reaction

Based on this publication a detailed look at this new chemistry was taken. Thus, different substituted silanes were tested regarding their reactivity towards acrylates. For further investigations silane-acrylate networks were formed using difunctional monomers and a synthesised difunctional silane. A comparable thiol-ene system was used as reference material. The photopolymer networks were characterised towards their curing behaviour (real-time-IR-photorheometry) and their thermo-mechanical properties (DMTA) were studied as well.