Study On Preparation And Properties Of Dual Crosslinked Polyacrylic Acid Hydrogels With Ultrahigh Mechanical Strength And Self-Healing Properties

The biological cartilage tissue in the human body is a natural hydrogel with high water content,good flexibility,good mechanical properties and friction resistance.Synthetic hydrogels have similar properties to human cartilage tissue with good biocompatibility,environmental sensitivity and lubricity,resulting in hydrogels have potential applications in biomedical,tissue engineering and smart devices.On the other hand,the low mechanical properties of traditional hydrogels that limited the application of hydrogels in biomedical applications,the irreversibility of chemical cross-linking leads to poor repair performance,which affects the application of the hydrogels in biological tissue engineering.Among PAAc hydrogels have been studied more by covalently cross-linking PAAc,the preparation process is simple and the cycle is short.However,the mechanical properties of the synthesized hydrogels are poor,but through the introduction of physical cross-linking means to crosslink PAAc,not only the gel has good mechanical properties,but also has repair properties.In this paper,ionic/covalent hybrid dual cross-linked PAAc hydrogels(PAAc(MBAA+Fe³⁺))and hydrophobic/ionic physical dual cross-linked PAAc hydrogels(SHPAAc-Fe³⁺)were prepared based on the dual cross-linked single-polymerization method.The destruction mechanism,environmental sensitivity and shape memory of PAAc(MBAA+Fe³⁺)gels were studied.At the same time,the toughening mechanism,self-healing property and self-healing property of SHPAAc-Fe³⁺gel were discussed.Through the regulation of the salt solution,the mechanical properties of the PAAc(MBAA+Fe³⁺)hydrogels are greatly improved with tensile strength of 1.79 MPa and elongation at break of 1320.9%.And the hydrogels are not sensitive to the notch,and the notched gels is stretched,the gel will not break along the notch rapidly,and the tear energy of the gels can reach 1.69 KJ m^-2.The destruction behavior of hydrogels conforms to the principle of“sacrificial bond”destruction.The internal structure of the gels gradually changes during the stretching process and undergoes two stages:?i?ionic cross-linked network destruction,?ii?covalent cross-linked network destruction.Ionic/covalent dual cross-linked hydrogels have better self-healing and self-healing properties,that gels can self-repairing and self-healing at room temperature.We have prepared the SHPAAc-Fe³⁺hydrogels.The most characteristic of this gels are the interaction between the"hard"network formed by the coordination of-COO^-on the Fe³⁺and the"soft"network formed by the interaction of hydrophobic units copolymerization between PAAc molecular chains.This hydrogels have a tensile strength of 1.08 MPa and an elongation at break of 3800%.Hydrogels not only have excellent mechanical properties,but also have self-healing properties and self-healing properties.The micro-destructive gels was placed under room temperature and normal pressure for 60 mins,the mechanical properties of the gels could be restored to 100%of the initial performance without any external stimulus.Whereas,the micro-destructive gels splines are placed in a 50?environment for 15 mins,and the mechanical properties of the splines can also be restored to 100%of the initial performance.