Build Tough Hydrogels with Sacrificial Bonds by Professor Jian Ping Gong, Hokkaido University

Speaker
Dr. Jian Ping Gong
Distinguished Professor, Hokkaido University

Title:
Build Tough Hydrogels with Sacrificial Bonds

Abstract: 

Hydrogels, consisting of cross-linked macromolecules and water, are soft and wet materials. As a combination of solid and liquid components, hydrogels have a high permeability to small molecules and undergo reversible volume change by exuding or absorbing water in response to a wide range of stimuli, such as light, temperature, pH, ionic strength, chemical reactions. In the past three decades, sensing and actuating properties of hydrogels have been extensively studied based on the volume changes. Owing to the similarity between hydrogels and soft tissues, recently, bulk hydrogels have drawn great attention as biomaterials, such as extra-cellular matrix, artificial bio-organs, and phantom tissues in medical device development.

However, conventional hydrogels, which are usually composed of single network (SN) of hydrophilic polymer, are soft, weak, and brittle. Invention of double network concept makes it possible to develop strong and tough hydrogels of various physical/chemical functions [1,2]. The toughness of the double-network hydrogels is due to the internal rupture of the fragile first network which dissipates energy and enhances the crack propagation resistance [3]. That is, the brittle network serves as sacrificial bonds. This fundamental toughening mechanism of DN gels is universal for developing tough materials. Significant efforts are underway to synthesize tough hydrogels with a full recovery of the internal fractured structure by using reversible sacrificial bonds [4-6]. Efforts have also been made on surface self-healing of tough hydrogels. In this talk, I will present current work on the development of tough and self-healing hydrogels using reversible sacrificial bonds, and their potential applications[7].

References
1) Gong, J. P., Katsuyama, Y., Kurokawa, T. & Osada, Y. Double-network hydrogels with extremely high mechanical strength. Adv. Mater. 15, 1155 (2003).
2) Nakajima, N., Sato, H., Zhao, Y., Kawahara, S., Kurokawa,T., Sugahara, K., Gong, J. P., A Universal Molecular Stent Method to Toughen any Hydrogels Based on Double Network Concept. Adv. Func. Mat. 22, 4426 (2012).
3) Gong, J. P. Why are double network hydrogels so tough? Soft Matter 6, 2583 (2010).
4) Haque, M. A., Kurokawa, T., Kamita, G., Gong, J. P. Lamellar bilayers as reversible sacrificial bonds to toughen hydrogel: hysteresis, self-recovery, fatigue resistance, and crack blunting. Macromolecules 44, 8916 (2011).
5) Sun, T. L., Kurokawa, T., Kuroda, S., Ihsan, A. B. Akasaki, T., Sato, K., Haque, M. A., Nakajima, T., Gong, J. P. Physical Hydrogels Composed of Polyampholytes Demonstrate High Toughness and Viscoelasticity, Nature Materials, 12, 932 (2013).
6) Luo, F., Sun, T. L., Nakajima, T., Kurokawa, T., Zhao, Y., Sato, K., Ihsan, A., B., Li, X. F., Guo, H. L., Gong, J. P. "Oppositely Charged Polyelectrolytes form Tough, Self-healing and Rebuildable Hydrogels," Advanced Materials, 27, 2722 (2015).
7) J. P. Gong, “Materials both Tough and Soft”, Science 344, 161(2014).