The Preparation And Characterization Of Chitosan/Graphene Oxide/PVA Ternary Composite Hydrogel

The application of pure Polyvinyl alcohol (PVA) hydrogel is limited due to its poor mechanical properties and single response. In order to improve the mechanical property of pure PVA hydrogel, the graphene oxide (GO) was introduced into the PVA hydrogel matrix as the filler and the effect of GO on the properties of the composite hydrogel was studied. Based on this, chitosan (CS) was added into the matrix of GO/PVA composite hydrogel to improve the pH sensitivity, and the CS/GO/PVA ternary composite hydrogel with amphoteric pH sensitivity was successfully prepared. Specific contents are as follows:The GO/PVA composite hydrogel was prepared by physical crosslinking and cyclic freezing-thawing method. XRD results showed that GO solution and PVA solution were mixed with continuous stirring, which the GO was dispersed in PVA matrix. SEM results revealed that a network structure was formed between the GO and PVA matrix, and the pore size of the network structure gradually increased with the increase of GO content. Compression test demonstrated that the introduction of GO can significantly improve the compressive properties of the composite hydrogel. Compared with pure PVA hydrogel, a 227% increase in compressive strength of GO/PVA composite hydrogel from 0.22 to 0.72 MPa, when the content of GO was 1wt%. At the same time, the presence of small amount GO caused the composite hydrogel has a certain degree of pH sensitivity. Especially, the equilibrium swelling ratio of the composite hydrogel significantly increased in the alkaline solution.In order to improve the pH sensitivity of GO/PVA hydrogel, CS/GO/PVA ternary composite hydrogel was prepared though physical crosslinking and cyclic freezing-thawing method using the blend of CS, GO and PVA solutions. The results of XRD and SEM showed that CS was dispersed in GO/PVA matrix and the double network was formed via hydrogen bonding. TGA curve demonstrated that the addition of CS also can improve the thermal decomposition temperature and enhance the thermal stability of the ternary composite hydrogel.With 0.5wt% CS, the decomposition temperature of CS/GO/PVA ternary composite hydrogel reached to 350℃, which was increased 90℃ compared to GO/PVA composite hydrogel. The results showed that the compressive properties of CS/GO/PVA ternary composite hydrogels was higher than that of GO/PVA composite hydrogels. The compressive strength reached the most (0.88MPa), when the CS content came to 1.5wt%. Compared with GO/PVA composite hydrogels, compressive strength of ternary composite hydrogel increased by 330%.Furthermore,CS/GO/PVA ternary composite hydrogel has the amphoteric pH-sensitivity, namely anionic and cationic. Thus, this properties promoted the responsive ability of ternary composite hydrogel with the pH changes of external environment.