Abstract：
Recent research on mechano-radicals has provided valuable insights into self-growth and adaptive responsive materials. Typically, mechanophores must remain inert in the absence of force but respond quickly to external tension before other linkages within the polymer network. Azo compounds exhibit promising combinations of mechanical stability and force-triggered reactivity, making them widely used as mechano-radicals in force-responsive materials. However, the activation conditions and behavior of azo compounds have yet to be quantitatively explored. In this study, we investigated the mechanical strength of three azo compounds using single-molecule force spectroscopy. Our results revealed that these compounds exhibit rupture forces ranging from ~500 to 1000 pN, at a loading rate of 3×104 pN s-1. Importantly, these mechanophores demonstrate distinct kinetic properties. Their unique mechanical attributes enable azo bond scission and free radical generation before causing major polymer backbone damage of entire material during polymer network deformation. This fundamental understanding of mechanophores holds significant promise for the development of self-growth materials and their related applications.
摘要：
最近对机械自由基的研究为自我生长和自适应响应材料提供了有价值的见解。通常,在没有力的情况下，机械载体必须保持惰性，但在聚合物网络内的其他连接之前，对外部张力迅速做出反应。偶氮化合物表现出机械稳定性和力触发反应性的有希望的组合，使它们广泛用作力响应材料中的机械自由基。然而,偶氮化合物的活化条件和行为还有待定量探索。在这项研究中,我们使用单分子力谱研究了三种偶氮化合物的机械强度。我们的结果表明，这些化合物表现出~500到1000pN的断裂力，加载速率为3×104pNs-1。重要的是,这些机械载体表现出独特的动力学特性。它们独特的机械属性使偶氮键断裂和自由基产生,然后在聚合物网络变形期间引起整个材料的主要聚合物骨架损坏。对机械载体的这种基本理解对于开发自生长材料及其相关应用具有重要意义。
