Tough and Self-Healing Hydrogels from Polyampholytes

Abstract

Polyampholyte (PA) hydrogels have attracted great attention as an innovative material having tough, self-healing, and viscoelastic behavior. PA hydrogels are synthesized using one-step radical polymerization of equal amounts of oppositely charged ionic monomers at a very high monomer concentration. They have 50–70 wt% of water at an equilibrium state, much lower than that of conventional hydrogels that usually have a high-water content (>80%). They are strongly viscoelastic and have a high toughness (fracture energy of 1,000–4,000 J/m2), a high modulus (0.01–8 MPa), a high failure strain (150–1,500%), and a failure stress (0.1–2 MPa), together with 100% self-recovery and a high self-healing efficiency behavior. These excellent mechanical performances are comparable to that of rubbers, most tough double-network hydrogels, and soft bio-tissues. The extensive experimental studies show that these multiple mechanical properties are related to the formation of dynamical features of inter- and intra-chain ionic bonds, and this study opens a common strategy to develop tough and self-healing hydrogels.