Green Approach To Robust,Tough Hydrogel And Synergistic Regulation Of Its Mechanical Properties

As a kind of soft material with high water content,hydrogels have broad application prospects in many fields due to their widely adjustable physical and chemical properties and good biocompatibility.The rapid development of the application of hydrogel materials has prompted researchers to seek more advanced polymerization methods to prepare hydrogels and optimize their properties.However,the currently reported hydrogel preparation methods still have problems such as cumbersome operation steps,long reaction time,and low synthesis efficiency.Hydrogels synthesized by traditional methods have a single and uneven network structure,resulting in weak mechanical strength of hydrogels and difficulty in regulation,which restricts the research and application of hydrogels.In view of this,this project aims to explore a fast,efficient,green and mild reaction method,improve the mechanical properties of hydrogels,and expand the application of hydrogels in related fields.This topic mainly carries out the following work.（1）PVA/CS/MXene hydrogel with anisotropic structure was designed and synthesized by solvent-regulated method.Firstly,the effects of water,hydrochloric acid,citric acid and acetic acid on the orientation of PVA hydrogel network structure were investigated.The results showed that the spatial extension of ternary acid anions played an important role in the formation of directional microstructure.Secondly,based on PVA/CS double network hydrogel,functional two-dimensional nanomaterial MXene was added to investigate its effect on the formation of hydrogel microstructure.The oriented structure not only makes the PVA/CS/MXene-CA hydrogel have outstanding mechanical properties,but also forms a special mass transfer channel inside the hydrogel,giving the hydrogel excellent conductivity.The sensor assembled by the hydrogel can monitor human movement in real time,including large-scale movements such as joints,small activities such as frowns,and ECG activities.Therefore,the new method of constructing anisotropic hydrogels proposed in this work provides a useful reference for the preparation and application of hydrogel soft materials.（2）A rapid ultrasound-induced polymerization method based on the reducibility of MXene was designed.Polyacrylamide-sodium alginate（PAM-SA）hydrogels were prepared by ultrasound-induced redox reaction using MXene nanosheets as reductant and potassium persulfate as oxidant.Firstly,MXene,as a crosslinking point,transfers the external force acting on the hydrogel to the adjacent polymer chain,which can effectively dissipate energy and realize the toughening of the hydrogel.Secondly,the hydrogel was immersed in calcium acetate solution,so that Ca²⁺ions continued to penetrate into the hydrogel network,and then coordinated with SA to form a double crosslinking network.The controlled release of Ca Ac₂ ensures the continuous penetration of Ca²⁺into the PAM-SA network,avoiding the rapid formation of a dense SA-Ca²⁺coordination shell on the hydrogel surface.Both MXene and Ca²⁺were used as crosslinking points.Variation of the content can effectively change the crosslinking density and achieve synergistic regulation of the mechanical properties of the hydrogel.Finally,MXene and Ca²⁺can endow the hydrogel with excellent electrical conductivity,which is helpful for its application in the field of flexible sensors.（3）A series of K-carrageenan/polyvinyl alcohol/MXene（KC/PVA/MXene）hydrogels with excellent mechanical properties were prepared by a simple,efficient and controllable hydrothermal method,which avoided the complex synthesis and purification process,and improved the biocompatibility of the hydrogel.In addition,the effects of different soaking time in borax solution on the hydroxyl group of PVA and the crosslinking degree of borax were investigated,and the formation mechanism and optimal preparation conditions of hydrogels were investigated.The KC rigid network and PVA flexible network form a dual network structure,and the dynamic reversible borate ester bond between PVA and borax further improves the toughness of the hydrogel.In addition,MXene is uniformly distributed in the hydrogel,making it have significant conductivity.The results show that the KC/PVA/MXene-B hydrogel synthesized in this section has important potential in the field of human multi-scale motion monitoring.