Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland.
Department of Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Str. 2a, 5020 Salzburg, Austria.
J Am Chem Soc. 2021 Nov 17;143(45):18859-18863. doi: 10.1021/jacs.1c10004. Epub 2021 Nov 4.
Covalent mechanophores display the cleavage of a weak covalent bond when a sufficiently high mechanical force is applied. Three different covalent bond breaking mechanisms have been documented thus far, including concerted, homolytic, and heterolytic scission. Motifs that display heterolytic cleavage typically separate according to non-scissile reaction pathways that afford zwitterions. Here, we report a new mechanochromic triarylmethane mechanophore, which dissociates according to a scissile heterolytic pathway and displays a pronounced mechanochromic response. The mechanophore was equipped with two styrenylic handles that allowed its incorporation as a cross-linker into poly(,-dimethylacrylamide) and poly(methyl acrylate--2-hydroxyethyl acrylate) networks. These materials are originally colorless, but compression or tensile deformation renders the materials colored. By combining tensile testing and transmittance measurements, we show that this effect is related to scissile cleavage leading to colored triarylmethane carbocations.
共价机械增感剂在受到足够高的机械力时会显示出弱共价键的断裂。迄今为止，已经记录了三种不同的共价键断裂机制，包括协同、均裂和异裂。显示异裂断裂的基序通常根据非裂解反应途径分离，形成两性离子。在这里，我们报告了一种新的机械变色三芳基甲烷机械增感剂，它根据可裂解的异裂途径解离，并显示出明显的机械变色响应。该机械增感剂配备了两个苯乙烯基手柄，允许其作为交联剂掺入聚（，-二甲基丙烯酰胺）和聚（甲基丙烯酸甲酯-2-羟乙基丙烯酸酯）网络中。这些材料最初是无色的，但压缩或拉伸变形会使材料着色。通过结合拉伸测试和透光率测量，我们表明这种效应与导致有色三芳基甲烷碳正离子的可裂解裂解有关。
