Light-triggered radical silane-ene chemistry using a monoalkyl substituted bis(trimethylsilyl)silane

Abstract

Chain transfer agents (e.g., thiols) enrich radical photopolymerization for use in advanced applications such as stereolithography, optical materials, and biomedicine. Resulting thiolene-based photopolymers exhibit numerous benefits such as tunable thermomechanical properties, and give access to spatially resolved functional materials. Silane-ene chemistry could serve as alternative to this popular thiol-ene approach. A monosubstituted bis(trimethylsilyl)silane (MSiH) is synthesized by a simple one pot procedure. Photoinitiated radical silane-ene chemistry has been performed with multiple enes and the conversions are assessed by 1H NMR spectroscopy. Compared to the most reactive silane from literature, tris(trimethylsilyl)silane (TTMSSiH), the radical reactivity of MSiH is reduced in all tested formulations, but the possibility for further functionalization and accessibility of multifunctional MSiH-derivatives is upheld. A silane-acrylate formulation is found to be most promising. In comparison to a thiolacrylate system, a more uniform conversion of the chain transfer agent and acrylate is shown for the silaneacrylate formulation with MSiH. The promising results for the silane-acrylate system are confirmed by further tests (i.e., NMR spectroscopy, GPC, and MALDI MS), giving additional information on molecular weight regulation and radical mechanism. First MSiH-based photopolymer networks have been fabricated and analyzed via DMTA, thus paving the way for future silane-acrylate networks.