英国曼彻斯特大学Leigh, David A.团队报道了打结聚合物的机械断裂。相关研究成果于2024年4月22日发表在国际顶尖学术期刊《自然—化学》。

分子结和缠结在生物和合成聚合物链中随机自发地形成。众所周知，宏观材料，如绳索，会因结的存在而显著减弱，但到目前为止，还不清楚类似的行为是否会在分子水平上发生。

该文中，研究表明，聚合物链中定义明确的单结的存在大大增加了聚合物在溶液中张力下（≥2.6倍更快）的断裂速率，因为拉紧结引起的聚合物主链的变形激活了原本不活跃的共价键。打结链断裂时形成的片段不同于类似但未打结的聚合物断裂时产生的片段。

该研究提供了实验证据，证明打结可以提高聚合物的机械断裂率。它还表明，打结设计可以用于产生迄今为止所描述的最具反应性的机械载体，为增加其他惰性官能团的反应性提供了机会。

附：英文原文

Title: Mechanical scission of a knotted polymer

Author: Zhang, Min, Nixon, Robert, Schaufelberger, Fredrik, Pirvu, Lucian, De Bo, Guillaume, Leigh, David A.

Issue&Volume: 2024-04-22

Abstract: Molecular knots and entanglements form randomly and spontaneously in both biological and synthetic polymer chains. It is known that macroscopic materials, such as ropes, are substantially weakened by the presence of knots, but until now it has been unclear whether similar behaviour occurs on a molecular level. Here we show that the presence of a well-defined overhand knot in a polymer chain substantially increases the rate of scission of the polymer under tension (≥2.6× faster) in solution, because deformation of the polymer backbone induced by the tightening knot activates otherwise unreactive covalent bonds. The fragments formed upon severing of the knotted chain differ from those that arise from cleavage of a similar, but unknotted, polymer. Our solution studies provide experimental evidence that knotting can contribute to higher mechanical scission rates of polymers. It also demonstrates that entanglement design can be used to generate mechanophores that are among the most reactive described to date, providing opportunities to increase the reactivity of otherwise inert functional groups.

DOI: 10.1038/s41557-024-01510-3

Source: https://www.nature.com/articles/s41557-024-01510-3