Zhang Wenlei, Hu Jian, Tang Jingda, Wang Zhongtong, Wang Jikun, Lu Tongqing, Suo Zhigang
State Key Lab for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics, Department of Engineering Mechanics, Xi'an Jiaotong University, Xi'an 710049, China.
John A. Paulson School of Engineering and Applied Sciences, Kavli Institute for Bionano Science and Technology, Harvard University, Cambridge, Massachusetts 02138, United States.
ACS Macro Lett. 2019 Jan 15;8(1):17-23. doi: 10.1021/acsmacrolett.8b00788. Epub 2018 Dec 17.
Hydrogels of numerous chemical compositions have achieved high fracture toughness on the basis of one physical principle. As a crack advances in such a hydrogel, a polymer network of strong bonds ruptures at the front of the crack elicits energy dissipation in the bulk of the hydrogel. The constituent that dissipates energy in the bulk of the hydrogel is called a . A hypothesis has emerged recently that tougheners increase fracture toughness greatly but contribute little to fatigue threshold. Here we ascertain this hypothesis by studying hydrogels of two kinds, identical in all aspects except for tougheners. A Ca-alginate/polyacrylamide hydrogel has ionic bonds, which act as tougheners, resulting in a toughness of 3375 J/m and a threshold of 35 J/m. A Na-alginate/polyacrylamide hydrogel has no ionic bonds, resulting in a toughness of 169 J/m and a threshold of 17 J/m. These results motivate a discussion on the development of fatigue-resistant hydrogels.
基于一种物理原理，许多化学成分的水凝胶都具有较高的断裂韧性。当裂纹在这种水凝胶中扩展时，裂纹前端的强键聚合物网络破裂，会在水凝胶主体中引发能量耗散。在水凝胶主体中耗散能量的成分被称为增韧剂。最近出现了一种假说，即增韧剂能大幅提高断裂韧性，但对疲劳阈值贡献不大。在这里，我们通过研究两种除增韧剂外各方面都相同的水凝胶来验证这一假说。一种海藻酸钙/聚丙烯酰胺水凝胶具有离子键，这些离子键起到增韧剂的作用，其韧性为3375 J/m，阈值为35 J/m。一种海藻酸钠/聚丙烯酰胺水凝胶没有离子键，其韧性为169 J/m，阈值为17 J/m。这些结果引发了关于抗疲劳水凝胶开发的讨论。
