Liu Chang, Kadono Hirokazu, Mayumi Koichi, Kato Kazuaki, Yokoyama Hideaki, Ito Kohzo
Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
ACS Macro Lett. 2017 Dec 19;6(12):1409-1413. doi: 10.1021/acsmacrolett.7b00729. Epub 2017 Dec 4.
In this study, the quasi-static fracture behavior of slide-ring gels (SR gels), in which movable cross-links can slide on polymer chains, is for the first time investigated and compared to that of conventional polymer gels with fixed cross-links (FC gels). For the usual FC gels, there is a trade-off relation between toughness (fracture energy [Formula: see text]) and stiffness (Young's modulus ): with increasing cross-linking density, the Young's modulus increases, while fracture energy [Formula: see text] decreases. However, SR gels show an unusual fracture behavior that contradicts this trade-off relation. The fracture energy of SR gels is independent of the Young's modulus, in other words, the cross-linking density; moreover, it rises with increasing slidable range of movable cross-links on polymer chains. A new molecular model is proposed by attributing the unusual fracture properties of SR gels to the relative sliding movement between polymer chains and cross-links. Utilizing this concept, simultaneous fulfillment of high stiffness and high toughness in polymer gels can be realized.
在本研究中，首次对滑动环凝胶（SR凝胶，其中可移动交联键能在聚合物链上滑动）的准静态断裂行为进行了研究，并与具有固定交联键的传统聚合物凝胶（FC凝胶）的准静态断裂行为进行了比较。对于常见的FC凝胶，韧性（断裂能[公式：见原文]）和刚度（杨氏模量）之间存在权衡关系：随着交联密度的增加，杨氏模量增大，而断裂能[公式：见原文]减小。然而，SR凝胶表现出与这种权衡关系相矛盾的异常断裂行为。SR凝胶的断裂能与杨氏模量无关，换句话说，与交联密度无关；此外，它随着聚合物链上可移动交联键可滑动范围的增加而升高。通过将SR凝胶的异常断裂特性归因于聚合物链和交联键之间的相对滑动运动，提出了一种新的分子模型。利用这一概念，可以实现聚合物凝胶同时具备高刚度和高韧性。
