Preparation And Properties Of Ionic Conductive Hydrogels With High Strength,Toughness And Wear Resistance Based On Pre-tensile Process

As a kind of functional polymer material with both flexibility and conductivity,conductive hydrogel has been widely concerned in the fields of artificial electronic skin,flexible wearable devices,soft robots,health monitoring and so on.However,traditional hydrogels often have problems such as low mechanical strength,poor anti-fatigue stability,poor electrical conductivity and sensitivity.Therefore,this paper proposes a pretensile process strategy to prepare ionic conductive hydrogels with high strength,toughness,wear resistance and sensitivity.Using xanthan gum（XG）and polyvinyl alcohol（PVA）with both biocompatibility and mechanical flexibility as the main raw materials,ionic conductive hydrogel（PVA/XG/Na₃Cit）with dual network structure was prepared by freezing,prestretching and salting out technology.The effects of pretensile ratio on mechanical properties,water retention properties,swelling resistance,wear resistance and electrical properties of conductive hydrogel were systematically studied.On this basis,based on the principle of surface double diffusion,ionic conductive hydrogels with surface fold microstructure were constructed by prestretching technology,and the influence of surface fold morphology on the mechanical properties,electrical properties and sensing properties of conductive hydrogels was explored.Specific research contents and results are as follows:（1）Preparation and performance study of high-strength,toughness and wear-resisting ionic conductive hydrogels based on pre-tensile process:In order to improve the mechanical strength,anti-fatigue stability and other properties of conductive hydrogels,high-strength,toughness and wear-resisting ionic conductive hydrogels were prepared by pre-tensile process.Using xanthan gum（XG）and polyvinyl alcohol（PVA）with both biocompatibility and mechanical flexibility as the main raw materials,conductive hydrogels were prepared by freezing,prestretching and soaking sodium citrate（Na₃Cit）in salting out.The results show that when the pretensile ratio increases from 0 to 5%,the tensile fracture strength of the prepared conductive hydrogel increases from 3.0 MPa to7.5 MPa,the wear resistance increases from 5 MPa to 6 MPa,and the conductive property also increases from 0.05 S/m to 0.75 S/m.The obtained conductive hydrogel can be well applied to human interactive systems.It can effectively monitor human throat swallowing,wrist bending and knuckle bending.The isotropy of molecular chains and the mechanical properties,wear resistance and electrical conductivity of conductive hydrogels were improved by prestretching.（2）Preparation and properties of ionic conductive hydrogels with folded microstructures:In order to solve the problem of poor sensing performance of conductive hydrogels,based on the above work,ionic conductive hydrogels with surface folded microstructures were constructed by predrawing technology,and the influence of surface fold morphology on mechanical,electrical and sensing properties of conductive hydrogels was explored.The results show that the surface folds can store more water molecules and form more hydrogen bonds,thus improving the mechanical properties of conductive hydrogels.Compared with smooth surface conductive hydrogels,the mechanical properties increase from 7 MPa to 8 MPa.In addition,the water molecules locked by the fold structure can bind more sodium citrate,leaving more sodium ions in the free state.Compared with the smooth surface conductive hydrogel,the electrical performance increases from 0.4 S/m to 0.8 S/m,and the sensitivity of GF increases from1 to 1.5.Due to the surface shape in use,the surface deformation of surface fold hydrogels will be larger with the same stimulation,and the sensor signal output will be more obvious,which broadens the application prospect of conductive hydrogels in wearable flexible electronic sensors.In this paper,based on the pretensile process strategy,using the biocompatibility and flexibility of PVA,ionic conductive hydrogels with semi-interpenetrating network structure were successfully prepared,and showed excellent mechanical properties,electrical properties and sensing properties.The introduction of surface folds further improves the sensing performance of conductive hydrogels and endows them with excellent mechanical and conductive properties.The obtained surface fold ionic conductive hydrogels show excellent sensing performance and chemical long-term stability,and can be used for human body motion monitoring under various deformations,showing an excellent prospect in the field of wearable flexible electronic sensors.