Stick–slip is a ubiquitous motion in the hydrogen bonding network, which confers the corresponding materials with excellent toughness and strength. The experimental study of the stick–slip mechanism remains challenging because of the complexity of stress accumulation and release. An ideal system for study of this motion should comprise a defined molecular structure and chain arrangement and strong intermolecular interactions. In this study, we detected the stick–slip motion at the single-molecule level in the hydrogen bonding network of polyamide (PA) single crystals through atomic force microscopy (AFM)-based single-molecule force spectroscopy. Our results show that a stiffer force-loading device can enhance the stick capacity by increasing the fracture force and facilitating stress release. We confirm that the chain rotates while slipping and the slip distance is dependent on the unit structure of the hydrogen bonding network.

中文翻译：

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聚酰胺单晶中单分子粘滑运动的直接观察

粘滑是氢键网络中无处不在的运动，它赋予相应的材料以优异的韧性和强度。由于应力积累和释放的复杂性，粘滑机制的实验研究仍然具有挑战性。研究这种运动的理想系统应包括明确的分子结构和链排列以及强的分子间相互作用。在这项研究中，我们通过基于原子力显微镜 (AFM) 的单分子力谱检测了聚酰胺 (PA) 单晶氢键网络中单分子水平的粘滑运动。我们的研究结果表明，更硬的力加载装置可以通过增加断裂力和促进应力释放来提高棒的能力。