Recent years have seen an increasing interest in the development of photo-polymerizable monomers providing low cytotoxicity and high impact resistance in their cured state. This fact can mainly be explained by the rapid progress in UV based additive manufacturing technologies such as stereolithography, digital light processing or 3D ink-jet printing which enables the fast, accurate and individual fabrication of biocompatible structures for hard tissue engineering. In this contribution, the versatility of the thiol-yne photo-click reaction for the fabrication of biocompatible photopolymers is shown at the example of tailor-made bi- and multifunctional alkyne and thiol monomers. This reaction leads to highly uniform polymeric networks exhibiting a sharp and defined thermal glass transition together with outstanding impact resistance  making these polymers interesting for challenging applications such as medical implants. A particular focus was set on the development of low odour thiols as promising alternatives to commercially available mercapto propionic acid derivates. Thiol-yne resins based on these monomers provide both, high reactivities comparable to those of acrylates and mechanical properties appropriate for the fabrication of medical devices in their cured state. The herein described monomers pave the way towards the fabrication of tailor-made photopolymers suitable for hard tissue engineering.
 Thiol-X Chemistries in Polymer and Materials Science Andrew B. Lowe and Christopher N. Bowman Editors, Royal Society of Chemistry, Cambridge 2013.