Fast reversible isomerization of merocyanine as a tool to quantify stress history in elastomers.
Fast reversible isomerization of merocyanine as a tool to quantify stress history in elastomers.
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将蛋白酶作为量化弹性体中应力史的工具的快速可逆异构化。
DOI：
10.1039/d0sc06157c
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发表时间：
2020-12-17
期刊：
影响因子：
8.4
通讯作者：
Creton C
中科院分区：
文献类型：
--
作者：
Chen Y;Yeh CJ;Guo Q;Qi Y;Long R;Creton C
提出了一种基于机械力化学的方法来检测和映射动态过程中的应力历史。将力敏分子探针螺吡喃（SP）作为交联剂引入到多网络弹性体（MNE）中。当加载这些机械致变色MNE时，SP经历众所周知的力激活反应，从而改变其在可见光范围内的吸收（可见蓝色）。这种SP到MC的转变在实验的时间范围内是不可逆的，并且颜色变化报告了活化分子的浓度。在随后的加载-卸载循环期间，MC经历快速和可逆的异构化，导致吸收光谱轻微偏移，并导致第二次颜色变化（蓝色至紫色，对应于加载-卸载循环）。通过使用色度对颜色变化进行量化，结果表明，卸载时观察到的确切颜色不仅是当前应力的特征（通过MC异构化引起的颜色变化报告），而且是材料在加载循环期间观察到的最大应力的特征（通过MC浓度变化引起的颜色变化报告）。我们表明，这两种颜色的变化可以明确地分开，我们用它们来映射的应力历史在加载和卸载过程中发生的裂纹打开和传播，打破材料。断裂样品上的彩色图与有限元模拟进行了比较，一致性非常好。提出了一种基于机械力化学的方法来检测和映射动态过程中的应力历史。
A mechanochemistry based approach is proposed to detect and map stress history during dynamic processes. Spiropyran (SP), a force sensitive molecular probe, was incorporated as a crosslinker into multiple network elastomers (MNE). When these mechanochromic MNEs are loaded, SP undergoes a well-known force-activated reaction to merocyanine (MC) changing its absorption in the visible range (visible blue color). This SP to MC transition is not reversible within the time frame of the experiment and the color change reports the concentration of activated molecules. During subsequent loading–unloading cycles the MC undergoes a fast and reversible isomerization resulting in a slight shift of absorption spectrum and results in a second color change (blue to purple color corresponding to the loading–unloading cycles). Quantification of the color changes by using chromaticity shows that the exact color observed upon unloading is characteristic not only of the current stress (reported by the shift in color due to MC isomerization), but of the maximum stress that the material has seen during the loading cycle (reported by the shift in color due to the change in MC concentration). We show that these two color changes can be separated unambiguously and we use them to map the stress history in the loading and unloading process occurring as a crack opens up and propagates, breaking the material. Color maps on fractured samples are compared with finite element simulations and the agreement is excellent. A mechanochemistry based approach is proposed to detect and map stress history during dynamic processes.
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