南京大学曹毅团队报道了偶氮苯作为光开关机械载体。相关研究成果发表在2023年12月5日出版的《自然—化学》。

偶氮苯作为一种光响应元件在材料科学中得到了广泛的研究。尽管一些研究已经研究了力诱导偶氮苯异构化，但力对偶氮苯断裂的影响尚未得到探索。

该文中，研究表明偶氮苯的光诱导结构变化也可以改变其断裂力，使其成为理想的光响应机械载体。利用单分子力谱和超声处理，发现顺式和反式对偶氮苯异构体具有不同的力学性能。从不同方向拉动偶氮苯区域异构体的动态力谱实验和量子化学计算表明，两种异构体的不同断裂力是由于拉动方向，而不是两种异构物之间的能量差异。

偶氮苯的这些力学特性可用于通过光照合理控制聚合物网络的宏观断裂行为。利用光诱导的构象变化来改变机械载体的机械响应，为设计具有光可调节机械性能的聚合物网络提供了一种有吸引力的方法。

附：英文原文

Title: Azobenzene as a photoswitchable mechanophore

Author: Li, Yiran, Xue, Bin, Yang, Jiahui, Jiang, Julong, Liu, Jing, Zhou, Yanyan, Zhang, Junsheng, Wu, Mengjiao, Yuan, Yuan, Zhu, Zhenshu, Wang, Zhi Jian, Chen, Yulan, Harabuchi, Yu, Nakajima, Tasuku, Wang, Wei, Maeda, Satoshi, Gong, Jian Ping, Cao, Yi

Issue&Volume: 2023-12-05

Abstract: Azobenzene has been widely explored as a photoresponsive element in materials science. Although some studies have investigated the force-induced isomerization of azobenzene, the effect of force on the rupture of azobenzene has not been explored. Here we show that the light-induced structural change of azobenzene can also alter its rupture forces, making it an ideal light-responsive mechanophore. Using single-molecule force spectroscopy and ultrasonication, we found that cis and trans para-azobenzene isomers possess contrasting mechanical properties. Dynamic force spectroscopy experiments and quantum-chemical calculations in which azobenzene regioisomers were pulled from different directions revealed that the distinct rupture forces of the two isomers are due to the pulling direction rather than the energetic difference between the two isomers. These mechanical features of azobenzene can be used to rationally control the macroscopic fracture behaviours of polymer networks by photoillumination. The use of light-induced conformational changes to alter the mechanical response of mechanophores provides an attractive way to engineer polymer networks of light-regulatable mechanical properties.

DOI: 10.1038/s41557-023-01389-6

Source: https://www.nature.com/articles/s41557-023-01389-6