Poly(triazole) Glassy Networks via Thiol-Norbornene Photopolymerization: Structure-Property Relationships and Implementation in 3D Printing

Photocurable thiol-norbornene resins featuring triazole-embedded norbornene monomers were developed, and the photopolymerized networks showed good to superior ductility in the glassy state with elongation-at-break ranging from 130 to 290% and tensile toughness as high as 57 MJ/m(3), demonstrating the value of triazoles in forming tough, glassy networks. Retained ductility was observed with two of the triazole/thiol-norbornene networks after physical aging at ambient temperature for 24 h, presumably due to mechanical rejuvenation under uniaxial straining, as the elongation-at-break of one of the networks decreased only to 170 from 290%, while the elongation-at-break of the other network remained the same. Though substantial embrittlement was observed for both networks after an even more extended time of physical aging, the prolonged ductility observed here was not previously seen with the poly(triazole) glassy networks. Finally, one of the triazole/thiol-norbornene resins developed here was successfully applied for fabricating three-dimensional (3D) structures in high precision using stereolithography-based 3D printing, highlighting the robustness of the thiol-norbornene photopolymerization.