Thiol–Trifluorovinyl Ether (TFVE) Photopolymerization: An On-Demand Synthetic Route to Semifluorinated Polymer Networks

Abstract

We report a first example of thiol−trifluorovinyl ether (thiol−TFVE) photopolymerization as a facile, cure-ondemand synthetic route to semifluorinated polymer networks. The thiol−TFVE reactionwhich proceeds via anti-Markovnikov addition of a thiyl radial to the TFVE groupwas elucidated using model small molecule reactions between phenyl trifluorovinyl ether and thiols with varying reactivity. These model reactions, characterized by 19 F NMR, 1 H NMR, and FTIR, also provided evidence of an oxygen-induced degradation pathway that may be circumvented by performing the reactions under an inert gas atmosphere. Photopolymerization of difunctional TFVE monomers with multifunctional thiols occurred with rapid kinetics and high conversions as observed with real-time FTIR and provided homogeneous semifluorinated polymer networks with narrow glass transitions as observed with dynamic mechanical analysis. The semifluorinated ether/thioether linkage incorporated into the polymer network yielded hydrophobic materials with increased and tunable T g , a 2-fold increase in strain at break, 4-fold increase in stress at break, and more than 5-fold increase in toughness relative to a thiol−ene material composed of a structurally similar hydrogenated ether/thioether linkage. The increased T g and mechanical toughness are attributed to the higher rigidity, hydrogenbonding capacity, and stronger carbon−carbon bonds of the semifluorinated ether/thioether relative to the hydrogenated ether/ thioether.

Vat Photopolymerization Additive Manufacturing of Tough, Fully Recyclable Thermosets

“…We note that the saw-like features in the stress–strain curves have been previously observed and likely arise due to plastic instabilities as crystalline lamellae are pulled apart, thus providing a mechanism to toughen the material. Even though toughness values are sporadically characterized in the thiol–ene photopolymerization literature and data is often incomplete, the toughest nonurethane rubbery thiol–ene networks in the literature have values of ≈10–50 MJ m –3 , ,− thus being comparable to the materials presented here. Furthermore, these materials are tougher and more extensible than the existing examples of 3D printed materials that have been degraded and repolymerized using DCB exchange − (see Table S9).…”

Tough Semicrystalline Thiol–Ene Photopolymers Incorporating Spiroacetal Alkenes

“…Outside of thiourethanes, however, there is an unmet need to expand the limited chemical library of thiol–ene materials with substantial mechanical robustness. To accentuate this, the toughest non-urethanethiol–ene photopolymer we found reported in the literature has a toughness near 12 MJ m –3 , which is approximately 33–50% that of the thiourethane photopolymers.…”