Self-healing Properties And Mechanism Of New Polyacrylic Acid Gel

The greatest difficulty of biomedical materials is biocompatibility.Tissue engineering hydrogels provide a highly swollen three-dimensional network environment that is very similar to the composition of organisms,which makes gel in the field of biomedical materials has been an unprecedented development.Traditional polyacrylic acid hydrogel（PAA gel）as a hydrogel for tissue engineering can form a better hydrogel in water,which has potential application prospect in tissue engineering field.But PAA gel mechanical properties are low,fragile,limiting its further application.The research focus on looking for the appropriate crosslinking agent or the synthesis of polyacrylic acid as the main body of the dual network hydrogel as tissue engineering hydrogel research hotspot..Cucurbituril[n]（CB[n]）is rigid and non-toxic,and instead of BIS as the crosslinking agent of PAA gel,a new type of gel material can be prepared.In this paper,the preparation,structure,swelling properties,mechanical properties,self-healing properties,swelling kinetics and self-healing mechanism of the gel were systematically studied.The results as follows:（1）CB[7]/PAA gel was prepared by using acrylic acid（AA）,water,CB[7],potassium persulfate（APS）and NaCl as raw materials.（C₃H₅O）₁CB[7]was prepared for the preparation of propylene oxide seven-membered ring（（C₃H₅O）₁CB[7]/PAA gel）.The optimum composition was determined as AA content 1mL;water volume 5m L;（C₃H₅O）₁CB[7]amount was 0.02g;APS amount was 0.02g.And the network forming force of two new self-healing gels were studied by IR and¹H NMR.The results show that multiple hydrogen bonds was determined as acting force in the two kinds of gel network.（2）The swelling properties of CB[7]/PAA gel and（C₃H₅O）₁CB[7]/PAA gel were studied.The results show that CB[7]/PAA gel can reach swelling equilibrium in about 48hours,and the equilibrium swelling rate is 800%.（C₃H₅O）₁CB[7]/PAA gel only 30 hours,the equilibrium swelling rate is 600%,the swelling equilibrium time is shortened by 60%,but the equilibrium swelling rate is reduced by 200%.（3）The mechanical properties of CB[7]/PAA gel and（C₃H₅O）₁CB[7]/PAA gel were studied.The results show that the maximum elongation of CB[7]/PAA gel is 4283%and the elastic modulus is 0.38.The maximum elongation of（C₃H₅O）₁CB[7]/PAA gel is 3267%and the elastic modulus is 0.04.（4）The self-healing properties of CB[7]/PAA gel and（C₃H₅O）₁CB[7]/PAA gel were observed.The results show that the maximum tensile elongation of CB[7]/PAA gel is about2.66 times.If（C₃H₅O）₁CB[7]/PAA gel be stretched after healing,a break will be produced.（5）The swelling kinetics of CB[7]/PAA gel was studied.The effects of pH and composition on the swelling kinetics were studied.The swelling mechanism of CB[7]/PAA gel was studied by non-Fickian diffusion model The self-healing mechanism of CB[7]/PAA gel was analyzed by combining mechanical properties and IR and ¹H NMR.The results show that the swelling kinetics of the gel system follow Schott’s second-order kinetics equation;the swelling rate of the gel in aqueous solution at pH=7.6 is significantly higher than that at pH=4 and pH=10,and the diffusion rate is at pH The swelling rate of CB[7]/PAA gel was the fastest when the amount of AA was 1.2mL,and the kinetic index of CB[7]/PAA gel was the highest The values of the gel rate constant K and the water diffusion coefficient D show that the swelling rate is consistent with the non-Fickian diffusion pattern.At the beginning of the swelling,the diffusion rate of the water molecules is comparable to that of the loops in the gel.The"mobile phase"and Hydrogen bond was reason for self-healing properties of.CB[7]/PAA gel...