Johannes Gutenberg University Mainz, Department of Chemistry, Duesberwerg 10-14, D-55128 Mainz, Germany.
Max Planck Institute for Polymer Research, D-55128 Mainz, Germany.
Soft Matter. 2022 Sep 21;18(36):6836-6847. doi: 10.1039/d2sm00666a.
Byssus threads of mussels have high resistance against abrasion in wave-swept habitats because of their outer cuticle, which is rich in amino acid dopa complexes with Fe ions. This stems from the transient nature of metal-ligand complexes that creates extra relaxation mechanisms. Inspired by this concept, in this work, supramolecular hydrogels based on poly(acrylic acid) functionalized with nitrocatechol groups are synthesized. Polymer chains are physically crosslinked nitrocatechol-Fe complexes. The hydrogels have different polymer volume fractions as well as different nitrocatechol : Fe molar ratios. The strength of the supramolecular crosslinks strongly depends on the pH of the medium. The dynamics of these hydrogels are studied by stress relaxation experiments followed by calculation of the relaxation time spectrum. Generally, samples have three relaxation modes, including dissociation of distinct metal-ligand complexes, reptation of sticky polymer chains, and disengagement of network segments from supramolecular aggregates and clusters. Such clusters hinder the terminal relaxation and potentially increase the stability of supramolecular hydrogels.
贻贝的足丝具有很高的抗磨损能力，这是因为它们的外壳富含具有 Fe 离子的氨基酸多巴复合物。这源于金属配体配合物的瞬态性质，它创造了额外的松弛机制。受此启发，在这项工作中，我们合成了基于聚（丙烯酸）的超分子水凝胶，该聚合物通过硝基儿茶酚基团官能化。聚合物链通过物理交联形成硝基儿茶酚-Fe 配合物。水凝胶具有不同的聚合物体积分数和不同的硝基儿茶酚：Fe 摩尔比。超分子交联的强度强烈依赖于介质的 pH 值。通过应力松弛实验并计算松弛时间谱来研究这些水凝胶的动力学。通常，样品有三种松弛模式，包括不同金属-配体配合物的解离、粘性聚合物链的蠕动以及网络段与超分子聚集体和团簇的脱离。这些团簇阻碍了末端松弛，并可能增加超分子水凝胶的稳定性。
