Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, 1700, Switzerland.
Chemistry and Physics of Materials, University of Salzburg, Jakob-Haringer-Strasse 2a, Salzburg, 5020, Austria.
Adv Sci (Weinh). 2023 May;10(13):e2206416. doi: 10.1002/advs.202206416. Epub 2023 Mar 19.
Mechanochromic materials alter their color in response to mechanical force and are useful for both fundamental studies and practical applications. Several approaches are used to render polymers mechanochromic, but they generally suffer from limitations in sensing range, capacity to provide quantitative information, and their capability to enable broad and simple implementation. Here, is it reported that these problems can be overcome by combining photonic structures, which alter their reflection upon deformation, with covalent mechanophores, whose spectral properties change upon mechanically induced bond scission, in hierarchically structured mechanochromic pigments. This is achieved by synthesizing microspheres consisting of an elastic polymer with spiropyran-based cross-links and non-close-packed silica nanoparticles. A strain of less than 1% can be detected in a shift of the reflection band from the photonic structure, while the onset strain for the conversion of the spiropyran into fluorescent merocyanine ranges from 30% to 70%, creating a broad strain detection range. The two responses are tailorable and synergistic, permitting the activation strain for the mechanophore response to be tuned. The mechano-sensing photonic pigments are demonstrated to be readily incorporated into different polymeric materials of interest and quantitatively probe spatially heterogeneous deformations over a large strain range.
机械变色材料会响应机械力而改变颜色，它们在基础研究和实际应用中都很有用。有几种方法可使聚合物具有机械变色性能，但它们通常在传感范围、提供定量信息的能力以及广泛而简单的实施能力方面存在局限性。在这里，研究人员报告说，这些问题可以通过将改变变形时反射率的光子结构与机械致变色团结合来克服，机械致变色团的光谱性质会在机械诱导的键断裂时发生变化，在分级结构的机械变色颜料中。这是通过合成由弹性聚合物和基于螺吡喃的交联剂以及非密堆积的二氧化硅纳米粒子组成的微球来实现的。在从光子结构的反射带的位移中可以检测到小于 1%的应变，而螺吡喃转化为荧光硫靛的起始应变范围为 30%至 70%，从而产生了广泛的应变检测范围。这两种响应是可调节的和协同的，可以调节机械致变色团响应的激活应变。机械感测光子颜料易于掺入到不同的感兴趣的聚合物材料中，并在大应变范围内定量探测空间不均匀的变形。
