Polyelectrolyte And Dynamic Covalent Bond Build Self-healing High-strength Hydrogel

Hydrugels are three-dimnsional network structure that swells rapidly in water and can maintain a large volume of water without dissolving in this swollen state.Hydrogels have good application prospects in artifical skin,artificial retinna,artificial cartilage,and vegetation water retention.However,traditional hydrogels are usually not strong nough and their mechanical strength is greatly damaged after being damaged.Therefore,it is of great significance to study high-strength,super-tough,self-healing hydrogels.Polyampholyte hydrogels are a type of hydrogels with high mechanical strength and self-healing,because there are multiple ionic bond crosslinks of different strengths between these polymer gel networks,wich constitutes a combination of strength and weakness Energy dissipation mechanism.In this paper,inspired by its energy dissipation and self-healing mechanisms.dynamic covalent bonds(acylhydrazone bonds,oxime bonds,etc.)are introduced into polyampholyte hydrogels,hoping to use dynamic covalent bonds It has the advantages of high strength and dynamic reversibility.It forms a new energy dissipation mode with ionic bonds,which can produce hydrogels with excellent mechanical properties and self-healing properties.Because of this,this paper carried out the following work:(1)Designed and synthesized various new structures of acylhydrazone bond cross-linking agent,water-soluble vinyl imidazole salt small molecule hydrazide monomer,macromolecular hydraide and macromolecular ketone carbonyl gel factor,combined with polymerization reaction and Condensation reaction,the corresponding hydrogel containing acylhydrazone bond was prepared,and its performance was tested.(2)The hydrogel can be formed by condensation reaction or polymerization reaction between the macromolecular hydrazide gel factor and the macromolecular ketone-based gel factor,but the strength of the reulting hydrogel is very weak.The possible reason is that the reaction activity of the hydrazide with the ketone carbonyl group is not enough,and the formed hydrazone bond is not stable enough.(3)The oxime bond cross-linking agent can significantly improve the tensile breaking strength and elongation of poly zwiterionic electrolyte hydrogel;But compared with the polyzwitterionic electrolyte hydrogel without additional crosslinking agent,although its tesile brealding strength is 3 times of the latter,its tensile breakng elongation is only 37%of the latter This indicates that the reversible exchange reaction of oxime bonds under neutral condtions is not active enough Prolonging the self-healing time and increasing the temperature are conducive to the self-healing of polyoxwitterionic electrolyte hydrogels crosslinked with oxime bonds.However,uneder neutral pH conditions,the reversible crosslinking of the oxime bond has no obvious advantages in improving the self-healing properties of polyzwitterionic electrolyte hydrogels.Due to the impact of the epidemic,a lot of research work.has not been completed in this paper.Emphasis should be placed on the mechanical and self-healing properties of polyampholyte hydrogels crosslinked with oxime bonds under slightly acidic conditions-Because slightly acidic conditions can activate the reversible exchange reaction of the oxime bond,improve its self-healing and mechanical properties;optimize the reaction conditions of the polyvinyl alcohol modified introduction of glycinamide pendant groups,and study the structure and performance of the gel.