Engelen Stéphanie, Dolinski Neil D, Chen Chuqiao, Ghimire Elina, Lindberg Charlie A, Crolais Alex E, Nitta Natsumi, Winne Johan M, Rowan Stuart J, Du Prez Filip E
Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281-S4, 9000, Ghent, Belgium.
Prtizker School of Molecular Engineering at, University of Chicago, IL 60637, Chicago, USA.
Angew Chem Int Ed Engl. 2024 Feb 26;63(9):e202318412. doi: 10.1002/anie.202318412. Epub 2024 Jan 24.
Vinylogous urethane (VU ) based polymer networks are widely used as catalyst-free vitrimers that show rapid covalent bond exchange at elevated temperatures. In solution, vinylogous ureas (VU ) undergo much faster bond exchange than VU and are highly dynamic at room temperature. However, this difference in reactivity is not observed in their respective dynamic polymer networks, as VU and VU vitrimers prepared herein with very similar macromolecular architectures show comparable stress relaxation and creep behavior. However, by using mixtures of VU and VU 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 VU vitrimers, but is very pronounced for vinylogous urea moieties. At low concentrations of VU , 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.
基于乙烯型氨基甲酸酯（VU）的聚合物网络被广泛用作无催化剂的玻璃态高聚物，其在高温下显示出快速的共价键交换。在溶液中，乙烯型脲（VU）的键交换比VU快得多，并且在室温下具有高度动态性。然而，在它们各自的动态聚合物网络中未观察到这种反应性差异，因为本文制备的具有非常相似大分子结构的VU和VU玻璃态高聚物表现出相当的应力松弛和蠕变行为。然而，通过在同一网络中使用VU和VU键的混合物，动态反应可以加速一个数量级。结果可以通过分子间氢键的作用来解释，氢键在VU玻璃态高聚物中不存在，但对于乙烯型脲部分非常明显。在低浓度的VU下，这些氢键充当共价键交换的催化剂，而在高浓度下，它们提供了一个由强非共价相互作用构成的普遍存在的乙烯型脲-氨基甲酸酯（VU）网络，导致相分离并抑制聚合物链的动力学。这为动态聚合物材料提供了一种直接的设计原则，同时展示了超分子和动态共价聚合物网络可能的加和与协同效应。
