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A. Hofecker, S. Orman, P. Knaack, S. Baudis, R. Liska:
"Low toxic monomers for 3D printing photopolymer-based bone substitutes";
Poster: European Polymer Congress 2019 (EPF 2019), Crete, Greece; 09.06.2019 - 14.06.2019; in: "European Polymer Congress 2019 (EPF 2019)", (2019), S. 848.

Acrylates and methacrylates are state-of-the-art monomers in photopolymerization of coatings, inkjet printing and they are also widely used in further advanced fields such as 3D-printing or tissue engineering, owing their large variety of commercially available building blocks, fast curing rates, and good storage stability.
However, these monomers have major drawbacks such as high irritancy and cytotoxicity, leading to a limited applicability for tissue engineering due to health and environmental issues.[1]
For that reason, the aim of our research is to design and synthesize monomers with a significant lower toxicity, good storage stability, similar or even better mechanical properties of the final polymer and sufficient reactivity towards radical polymerization.
Since crosslinked vinyl esters (including vinyl carbamates and vinyl carbonates) are known to degrade hydrolytically to non-toxic and FDA approved poly(vinylalcohol)[2], these building blocks were chosen for further studies concerning their photoreactivity and mechanical properties to consider the substitution of (meth)acrylates.
In order to obtain parameters, including gel point, double bond conversion and shrinkage stress, photopolymerization behavior of vinyl esters was characterized by realtime-near infrared-photorheology[3] (RT-NIR-Photorheology). As a lower photoreactivity compared to state-of-the-art monomers was observed, multifunctional thiols were used to boost their reactivity and regulate the network structure via thiol-ene chemistry.[4] Additionally, the mechanical properties of the photopolymerized specimens were examined by dynamic mechanical thermal analysis (DMTA), tensile tests and dynstat impact resistance tests. Owing to the variety of those non-toxic building blocks and different multifunctional thiols a broad range of different mechanical and degradation properties are available.
Preliminary in-vivo tests of these low toxic photopolymers in the femoral bone of rabbits showed no inflammation reaction and good vascularization after 12 weeks (Fig.1).[5] Current tests using sheep as large animal models will help to get a more realistic picture of the in-vivo performance of this new class of photopolymers and will set the foundation for in-depth clinical studies.[6]

Acrylates and methacrylates, photopolymerization, 3D-printing, tissue engineering, irritancy and cytotoxicity