Supertough,shape Memory,and Self-Healable PAA Hydrogels And Its Application In Soft Actuctors

Hydrogels are promising to be used for various applications in biomedicine,petrochemical,agriculture and etc.All of these applications require integrated performance in mechanics and functions.However,there still is a challenge to fabricate a hydrogel satisfying all of these requirements.So,the main purpose of this paper is to improve the mechanical strength and functions of PAA gels by introducing the ionic cross-linking network.The main works and results are as follows:1.A multiple shape memory and self-healing PAA-GO-Fe³⁺ hydrogel with supertough strength was synthesized containing dual physically crosslinked PAA network by GO and Fe³⁺.The first GO cross-linked hydrogel can be reversibly reinforced by immersing in FeCl₃/HCl and pure water and softened by immersing in HCl.Multiple shape memory capability was found depending on this unique feature.This hydrogel also exhibited perfect self-healing behavior and enhanced electrical conductivity.2.We reported a facile sticking method to prepare Janus bilayer and multilayer hydrogel actuators benefited from our special PAA gel.Combining two cross-linking of clay and BIS,we endowed the PAA gel with both toughness and adhesion.This PAA gel was reinforced by further cross-linked with Fe³⁺ ions to form the F-PAA gel.These hydrogels with different cross-linking density exhibited different swelling capabilities and moduli in the media of different pH and ionic strength,thus acted as ideal candidates for soft actuator to achieve specified actions.3.Based on the reversible ionic interactions between CS and PAA chains,we synthesized a PAA-CS composite hydrogel with satisfactory mechanical,self-healing and antibacterial capabilities.The PAA-CS composite hydrogel exhibited high antibacterial activites against escherichia coli,thus could be used for hydrogel wound dressing.When immersed in salt solutions,the PAA-CS composite hydrogel can be converted into high-mechanical DN hydrogels via the formation of CS chain-entanglement and PAA-Fe³⁺ networks.