Acrylate‐free tough 3D printable thiol‐ene thermosets and composites for biomedical applications

Polymer thermosets and composites based on rigid trizaine‐trione (TATO) alkene and thiol monomers show great promise as bone fixation materials and dental composites due to their ability to efficiently crosslink via thiol‐ene coupling chemistry into stiff and strong materials. In order to broaden the scope of these materials, a TATO thermoset was optimized for sterolithography (SLA) 3D printing through the addition of either a diluent (PETMP) and photo‐absorber (Sudan I), or the addition of a free radical inhibitor (pyrogallol). A 3D printable hydroxyapatite (HA) composite was also formulated by adding a combination of nano‐HA and micro‐HA particles, which were found to increase the thermal stability and modulus of the material, respectively. The modulus of the printed thermosets containing Sudan I and pyrogallol exceeded any previously published acrylate‐free thiol‐ene SLA resins, at 1.6 (0.1) and 1.85 (0.06) GPa, respectively. The printed HA composite formulation had a modulus of 2.4 (0.2) GPa. All three formulations showed a comparable resolution to a commercially available SLA resin and were non‐toxic toward Raw 264.7 and human dermal fibroblast cells. These results demonstrate the potential of TATO based SLA resins for the construction of strong, fully‐customizable, printed implants for biomedical applications. Thiol‐ene thermoset and composite resins developed for hard tissue repair are adapted for SLA 3D printing through the addition of either diluents, free radical inhibitors, or micro‐ and nano‐sized hydroxyapatite. The resulting printed materials display excellent biological profiles, while their mechanical properties exceed the thiol‐ene printed systems in the literature.