Thiol-Trifluorovinyl Ether (TFVE) Photopolymerization: An On-Demand Synthetic Route to Semifluorinated Polymer Networks
Polymer Science and Engineering
We report a first example of thiol–trifluorovinyl ether (thiol–TFVE) photopolymerization as a facile, cure-on-demand 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 19F NMR, 1H 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 Tg, 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 Tg and mechanical toughness are attributed to the higher rigidity, hydrogen-bonding capacity, and stronger carbon–carbon bonds of the semifluorinated ether/thioether relative to the hydrogenated ether/thioether.
Donovan, B. R.,
Ballenas, J. E.,
Patton, D. L.
(2016). Thiol-Trifluorovinyl Ether (TFVE) Photopolymerization: An On-Demand Synthetic Route to Semifluorinated Polymer Networks. Macromolecules, 49(20), 7667-7675.
Available at: https://aquila.usm.edu/fac_pubs/16932