Liu Jing, Yang Jiahui, Xue Bin, Cao Yi, Cheng Wei, Li Yiran
Collaborative Innovation Center of Advanced Microstructures, National Laboratory of Solid-State Microstructure, Key Laboratory of Intelligent Optical Sensing and Manipulation, Ministry of Education, Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China.
Department of Oral Implantology, Nanjing Stomatological Hospital, Medical School of Nanjing University, Nanjing, Jiangsu, 210008, China.
Chemphyschem. 2024 Aug 1;25(15):e202300880. doi: 10.1002/cphc.202300880. Epub 2024 Jun 15.
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 3×10 pN s. 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.
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,机械响应基团在没有外力的情况下必须保持惰性,但在聚合物网络中的其他键之前对外部张力快速响应。偶氮化合物展现出机械稳定性和力触发反应性的良好组合,使其在力响应材料中广泛用作机械自由基。然而,偶氮化合物的活化条件和行为尚未得到定量研究。在本研究中,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,这些化合物在3×10 pN s的加载速率下表现出约500至1000 pN的断裂力。重要的是,这些机械响应基团表现出独特的动力学特性。它们独特的机械属性使得在聚合物网络变形期间导致整个材料的主要聚合物主链损坏之前,偶氮键断裂并产生自由基。对机械响应基团的这种基本理解对自我生长材料及其相关应用的发展具有重大前景。