Herein, we demonstrated the synthesis of multifunctional alkyne building blocks from commercially available acrylate monomers exploiting the carbon and oxa Michael addition reaction. These compounds were obtained in decent yields and show similar or even higher photoreactivity than the initial acrylates. Importantly, selected thiol‐yne formulations can be processed by stereolithography and significantly outperform the corresponding acrylate in terms of modulus and toughness. The high compatibility of such cured materials with osteosarcoma cells makes these photopolymers interesting for hard tissue engineering.
Thiyl radicals were generated from aromatic S-thioformates by photolysis. The corresponding photo-initiated decarbonylation allows initiating polymerization reactions in both acrylate- and thiol-acrylate-based resin systems. Compared to aromatic thiols, the introduction of the photolabile formyl group prevents undesired reactions with acrylate monomers allowing photoinitiators (PIs) with constant reactivity over storage. To demonstrate the potential of S-thioformates as PIs, the bifunctional molecule S,S’-(thiobis(4,1-phenylene))dimethanethioate (2b) was synthesized, providing reactivity under visible light excitation. Consequently, acrylate-based formulations could successfully be processed by digital light processing (DLP)-based stereolithography at 405 nm in high resolution.
In recent years, dual‐cure chemistry has been exploited to realize interpenetrating networks (IPNs) that provide enhanced thermo‐mechanical properties. In this contribution, photoinduced curing of (meth)acrylates is used to build the desired 3D structure, whereas the thermally triggered polymerization reaction of 2H‐chromene functionalized building blocks is utilized to create the IPN. This strategy combines the advantages of traditional UV‐curable monomers with high‐performance thermosets. After the successful synthesis of the bispropargyl ether derivative, i.e., 4,4′‐(propane‐2,2‐diyl)bis((ethynyloxy)benzene), its thermally induced conversion to the corresponding 2H chromene functionalized prepolymer is studied by Fourier‐transform infrared spectroscopy and gel permeation chromatography. The network formation as well as the printability of various formulations containing different amounts of the thermo‐curable building block is investigated. The obtained IPNs provide enhanced thermo‐mechanical properties making these resins suitable for the additive manufacturing of functional 3D parts for high‐performance applications.
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