Improvement of Mechanical Strength and Fatigue Resistance of Double Network Hydrogels by Ionic Coordination Interactions

Abstract

Double network hydrogels (DN gels) are considered as one of the toughest soft materials. However, conventional chemically linked DN gels often lack high self-recovery and fatigue resistance properties due to permanent damage of covalent bonds upon deformation. Current strategies to improve self-recovery and fatigue resistance properties of tough DN gels mainly focus on the manipulation of the first network structure. In this work, we proposed a new design strategy to synthesize a new type of Agar/PAMAAc-Fe3+ DN gels, consisting of an agar gel as the first physical network and a PAMAAc-Fe3+ gel as the second chemical–physical network. By introducing Fe3+ ions into the second network to form strong coordination interactions, at optimal conditions, Agar/PAMAAc-Fe3+ DN gels can achieve extremely high mechanical properties (σf of ∼8 MPa, E of ∼8.8 MPa, and W of ∼16.7 MJ/m3), fast self-recovery (∼50% toughness recovery after 1 min of resting), and good fatigue resistance compared to properties of cyclic loading...