Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, Geneva 4 1211, Switzerland.
Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg 1700, Switzerland.
Nano Lett. 2021 Jan 13;21(1):543-549. doi: 10.1021/acs.nanolett.0c04027. Epub 2020 Dec 7.
Quantitative and anisotropic mechanochromism of polydiacetylene over nanoscale distances remains unaddressed even after 50 years of extensive research. This is because its anisotropic structure on substrates necessitates the application of both vertical and lateral forces (shear forces) to characterize it, whereas atomic force microscopy, which is the usual technique used to investigate nanoscale forces, is only capable of quantifying vertical forces. In this study, we address this lacuna by utilizing quantitative friction force microscopy that measures lateral forces. Our data confirm that polydiacetylene reacts only to lateral forces, , and disprove the previously claimed hypothesis that the edges of the polymer crystals exhibit higher force sensitivity than the rest of the crystal. In addition, we report a correlation between mechanochromism and thermochromism, which can be attributed to the fact that both work and heat are different means of providing the same transition energy.
即使经过 50 年的广泛研究，纳米尺度上的聚二乙炔的定量各向异性机械变色仍然没有得到解决。这是因为其在衬底上的各向异性结构需要同时施加垂直力和侧向力（剪切力）来进行表征，而原子力显微镜是通常用于研究纳米尺度力的技术，只能定量测量垂直力。在这项研究中，我们通过使用测量侧向力的定量摩擦力显微镜来解决这一空白。我们的数据证实，聚二乙炔仅对侧向力 做出反应，推翻了先前关于聚合物晶体边缘比晶体其余部分具有更高力敏感性的假设。此外，我们报告了机械变色和热致变色之间的相关性，这可以归因于功和热是提供相同跃迁能量的不同方式这一事实。
