| Hydrogels are a kind of polymer network system that uses water as dispersion medium.Owing to their high hydrophilicity and biocompatibility,hydrogels have been broadly applied in many fields,such as drug delivery,tissue engineering and sensors.Traditional hydrogels are easily damaged during use,so it is of great significance to prepare self-healing hydrogels.There have been many studies to prepare self-healing hydrogels by designing different functional monomers.Although these hydrogels have excellent mechanical properties,they often require complex chemical modification or introduction of non-natural macromolecular components.This drawback significantly limits their application in many fields.To address this problem,two novel natural polysaccharide polymers were used as the main body of the gel.In addition,in order to improve the mechanical properties of the self-healing hydrogel,another layer of network was introduced based on its original network to build a double-network(DN)hydrogel system.The specific research contents are as follows:(1)At first,locust bean gum(LBG)and gellan gum(Gg)powder were introduced into the borax solution.The LBG can be complexed with borax in aqueous solution to form borate ester bonds,imparting excellent self-healing properties to the hydrogel.Then,when the hydrogel is gradually cooled to room temperature,a hydrogen-bond-based double-helix structure can be formed in Gg.Therefore,the LBG/Gg DN hydrogel was prepared.ATR-FTIR spectra were used to characterize the formation of borate ester and hydrogen bonds.Tensile and rheological experiments show that the introduction of Gg can significantly improve the mechanical properties and fatigue resistance of hydrogels.Through a series of formulation and process optimization,it was found that when LBG,Gg,and borax were added at 4 wt%,1.5 wt%,and 0.2 wt%,respectively,the hydrogel reached a maximum self-healing efficiency of 99.1%after30 min at 80 ~°C.The corresponding tensile strength and elongation rate were 28.2 k Pa and 216%,respectively.Besides,since the borate-ester bonds exhibit p H-responsive behavior,the LBG/Gg DN hydrogels behave shape memory properties.(2)The guar gum(GG)/gellan gum(Gg)DN hydrogels based on borate-ester bonds in the GG network and hydrogen-bond-associated double-helix bundles in the Gg network were prepared by using two novel natural polysaccharide polymers.ATR-FTIR spectra were used to characterize the formation of borate ester and hydrogen bonds.Rheology indicates that the gel has frequency dependence and temperature sensitivity.The effect of Gg,borax and GG on mechanics and self-healing properties of DN hydrogels was studied through tensile experiments.It was found that when the concentrations of Gg,borax and GG were 1.5 wt%,0.12 wt%and 6 wt%,respectively,the hydrogel reached a tensile strength of 28.4 k Pa and a breaking elongation of 240%.The corresponding self-healing efficiency of stress and strain were 98.9%and 92.7%,respectively.In addition,the DN hydrogels have excellent electrical stability and can detect the movement of human joints. |
