Hydrogels are polymer networks swollen in water and, therefore, suitable for biomedical applications. For this purpose, hydrogels have to mimic the functionality and mechanics of natural tissues. In drug delivery, for example, the diffusion is crucial and can be controlled through targeted variation of the network mesh-size. In tissue engineering, on the other side, the mechanics plays a fundamental role and can be strengthened through the use of two interpenetrated polymer networks, realizing a double network, or with two dynamic motifs anchored in one common network, realizing a dual dynamic network (DDN). However, current knowledge encompasses mainly nonlinear rheological characterization of these networks. We intend to fill this gap and provide a systematic linear rheological study. To realize this strategy, we combine two supramolecular motifs in a common network, thereby realizing a comblike DDN with the ability to change the building blocks on demand. In our DDN, a tetra-poly(ethylene) glycol (pEG) (the first building block) is functionalized on each arm with two dynamic motifs: terpyridine capable of undergoing metal-complexation with different divalent metal ions, and a thermo-responsive unit consisting of poly(N-isopropylacrylamide) (pNIPAAm) (the second building block) that is capable of undergoing temperature-dependent nano-phase-separation. In particular, we change the molar mass of the tetra-pEG-terpyridine and the pNIPAAm grafted chains. In addition, we investigate two different metal ions that form complexes with the terpyridine. With this platform, we tune the elastic properties on demand, and we systematically study the structure–property relationships with oscillatory shear rheology in the linear regime.

中文翻译：

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梳状双动态聚合物网络的机械切换

水凝胶是在水中膨胀的聚合物网络，因此适用于生物医学应用。为此，水凝胶必须模仿天然组织的功能和力学。例如，在药物输送中，扩散至关重要，可以通过网络网格尺寸的目标变化来控制。另一方面，在组织工程中，力学起着基础性的作用，可以通过使用两个互穿的聚合物网络来加强双网络，或者将两个动态基序锚定在一个共同的网络中，实现双动态网络。 DDN）。然而，目前的知识主要包括这些网络的非线性流变表征。我们打算填补这一空白并提供系统的线性流变研究。为实现这一战略，我们将两个超分子基序结合在一个共同的网络中，从而实现了一个具有按需更改构建块能力的梳状 DDN。在我们的 DDN 中，四聚（乙二醇）（pEG）（第一个构件）在每个臂上被功能化，具有两个动态基序：三联吡啶能够与不同的二价金属离子进行金属络合，以及一个热响应单元由聚（N-异丙基丙烯酰胺）（pNIPAAm）（第二个组成部分），能够进行温度依赖性纳米相分离。特别是，我们改变了四聚乙二醇三联吡啶和 pNIPAAm 接枝链的摩尔质量。此外，我们研究了与三联吡啶形成络合物的两种不同金属离子。使用这个平台，我们可以按需调整弹性特性，并系统地研究结构-特性与线性状态下的振荡剪切流变学的关系。