Secondary interactions, such as hydrogen bonding or phase separation, can enhance the stability of dynamic covalent materials without compromising on desired dynamic properties. Here, we investigate the combination of multiple secondary interactions in dynamic covalent materials based on acylsemicarbazides (ASCs), with the aim of achieving tunable material properties. The effects of different ASC substituents on the dynamic covalent and hydrogen bonding capabilities were investigated in a small molecule study using a combined experimental and theoretical approach, and revealed the presence of cooperative hydrogen-bonding interactions in 2 directions in one of the derivatives. The different motifs were subsequently incorporated into polymeric materials. Combining ASC motifs capable of strong, multiple hydrogen bonding with a polydimethylsiloxane backbone introduces structure-dependent, ordered nanophase separation in polymeric materials. The thermo-mechanical properties of the materials reveal a strong dependance on the hydrogen-bonding structure and exact nature of the ASC bond. The dynamic behavior in bulk shows that bond exchange depends on the dissociation rate obtained from ASC model compounds, as well as the strength of the secondary interactions in these materials. Differences in hydrogen-bonding structures of the ASC motifs also cause differences in creep resistance of the materials. Interestingly, the materials with strong, ordered and cooperative hydrogen-bonded clusters show the highest creep resistance. Our results demonstrate that tuning both the dissociation rate and the secondary interactions by molecular design in dynamic covalent materials is important for controlling their thermal stability and creep resistance.

中文翻译：

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结构-性能关系指导酰基氨基脲基材料的动态性能


次级相互作用，如氢键或相分离，可以提高动态共价材料的稳定性，而不会影响所需的动态特性。在这里，我们研究了基于酰基氨基脲 （ASCs） 的动态共价材料中多种次级相互作用的组合，以实现可调的材料特性。在小分子研究中，使用实验和理论相结合的方法研究了不同 ASC 取代基对动态共价键和氢键能力的影响，并揭示了其中一个衍生物在 2 个方向上存在协同氢键相互作用。随后将不同的基序整合到聚合物材料中。将能够强多重氢键的 ASC 基序与聚二甲基硅氧烷主链相结合，可在聚合物材料中引入结构依赖性的有序纳米相分离。材料的热机械性能揭示了对氢键结构和 ASC 键的确切性质的强烈依赖性。本体动力学行为表明，键交换取决于从 ASC 模型化合物获得的解离速率，以及这些材料中次级相互作用的强度。ASC 基序的氢键结构的差异也会导致材料的抗蠕变性差异。有趣的是，具有强、有序和协同氢键簇的材料显示出最高的抗蠕变性。我们的结果表明，在动态共价材料中，通过分子设计来调节解离速率和次级相互作用对于控制其热稳定性和抗蠕变性很重要。