Vinylogous Urea—Urethane Vitrimers: Accelerating and Inhibiting Network Dynamics through Hydrogen Bonding
Vinylogous urethane (VUO) based polymer networks are widely used as catalyst‐free vitrimers that show rapid covalent bond exchange at elevated temperatures. In solution, vinylogous ureas (VUN) undergo much faster bond exchange than VUO and are highly dynamic at room temperature. However, this differ...
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Veröffentlicht in: | Angewandte Chemie International Edition 2024-02, Vol.63 (9), p.e202318412-n/a |
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Sprache: | eng |
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Zusammenfassung: | Vinylogous urethane (VUO) based polymer networks are widely used as catalyst‐free vitrimers that show rapid covalent bond exchange at elevated temperatures. In solution, vinylogous ureas (VUN) undergo much faster bond exchange than VUO and are highly dynamic at room temperature. However, this difference in reactivity is not observed in their respective dynamic polymer networks, as VUO and VUN vitrimers prepared herein with very similar macromolecular architectures show comparable stress relaxation and creep behavior. However, by using mixtures of VUO and VUN linkages within the same network, the dynamic reactions can be accelerated by an order of magnitude. The results can be rationalized by the effect of intermolecular hydrogen bonding, which is absent in VUO vitrimers, but is very pronounced for vinylogous urea moieties. At low concentrations of VUN, these hydrogen bonds act as catalysts for covalent bond exchange, while at high concentration, they provide a pervasive vinylogous urea ‐ urethane (VU) network of strong non‐covalent interactions, giving rise to phase separation and inhibiting polymer chain dynamics. This offers a straightforward design principle for dynamic polymer materials, showing at the same time the possible additive and synergistic effects of supramolecular and dynamic covalent polymer networks.
In solution, vinylogous urea (VUN) groups undergo much faster bond exchange than vinylogous urethanes (VUO), but this is not observed in their respective polymer networks. Surprisingly, blends of the two monomer types show increased network dynamics. The effects are correlated to hydrogen bonding, which catalyses covalent exchange and also reinforces networks by non‐covalent interactions. |
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ISSN: | 1433-7851 1521-3773 |
DOI: | 10.1002/anie.202318412 |