Wang Zhi Jian, Wang Shu, Jiang Julong, Hu Yixin, Nakajima Tasuku, Maeda Satoshi, Craig Stephen L, Gong Jian Ping
Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo 001-0021, Japan.
Department of Chemistry, Duke University, Durham, North Carolina 27708-0346, United States.
J Am Chem Soc. 2024 May 15;146(19):13336-13346. doi: 10.1021/jacs.4c01879. Epub 2024 May 2.
In recent decades, more than 100 different mechanophores with a broad range of activation forces have been developed. For various applications of mechanophores in polymer materials, it is crucial to selectively activate the mechanophores with high efficiency, avoiding nonspecific bond scission of the material. In this study, we embedded cyclobutane-based mechanophore cross-linkers (I and II) with varied activation forces () in the first network of the double network hydrogels and quantitively investigated the activation selectivity and efficiency of these mechanophores. Our findings revealed that cross-linker I, with a lower activation force relative to the bonds in the polymer main chain (/ = 0.8 nN/3.4 nN), achieved efficient activation with 100% selectivity. Conversely, an increase of the activation force of mechanophore II (/ = 2.5 nN/3.4 nN) led to a significant decrease of its activation efficiency, accompanied by a substantial number of nonspecific bond scission events. Furthermore, with the coexistence of two cross-linkers, significantly different activation forces resulted in the almost complete suppression of the higher-force one (i.e., I and III, / = 0.8 nN/3.4 nN), while similar activation forces led to simultaneous activations with moderate efficiencies (i.e., I and IV, / = 0.8 nN/1.6 nN). These findings provide insights into the prevention of nonspecific bond rupture during mechanophore activation and enhance our understanding of the damage mechanism within polymer networks when using mechanophores as detectors. Besides, it establishes a principle for combining different mechanophores to design multiple mechanoresponsive functional materials.
近几十年来，已经开发出100多种具有广泛活化力的不同机械响应基团。对于机械响应基团在聚合物材料中的各种应用而言，高效且选择性地激活机械响应基团，同时避免材料的非特异性断键至关重要。在本研究中，我们将具有不同活化力（）的环丁烷基机械响应基团交联剂（I和II）嵌入双网络水凝胶的第一个网络中，并定量研究了这些机械响应基团的激活选择性和效率。我们的研究结果表明，相对于聚合物主链中的键，交联剂I具有较低的活化力（/ = 0.8 nN/3.4 nN），能够以100%的选择性实现高效激活。相反，机械响应基团II的活化力增加（/ = 2.5 nN/3.4 nN）导致其激活效率显著降低，同时伴随着大量非特异性断键事件。此外，当两种交联剂共存时，显著不同的活化力几乎完全抑制了较高力的交联剂（即I和III，/ = 0.8 nN/3.4 nN），而相似的活化力则导致同时激活且效率适中（即I和IV，/ = 0.8 nN/1.6 nN）。这些发现为防止机械响应基团激活过程中的非特异性键断裂提供了见解，并增强了我们对使用机械响应基团作为探测器时聚合物网络内损伤机制的理解。此外，它还确立了一种组合不同机械响应基团以设计多种机械响应功能材料的原则。
