Preparation And Application Of Graphene-Based Self-Adhesive Conductive Hydrogel

As a soft and moisturizing material with a three-dimensional cross-linked network,hydrogels have been widely used in many fields.Among them,wearable and stretchable strain sensors have attracted great attention in various applications due to their convenient interaction with the human body.Generally,the adhesive conductive hydrogel has low strength and easily forms ice crystals at low temperatures,which greatly limits its application in the field of wearable flexible sensing.Therefore,it is of practical value to design an adhesive hydrogel with appropriate mechanical properties and excellent antifreeze performance.Pyrogallol is a phenolic substance commonly found in many edible plants(such as cocoa,nuts,peels,vegetables and medicinal plants).In recent years,many disciplines have focused on the adhesion of pyrogallol molecules,including flexible wearable electronics,energy storage,and medical equipment.In particular,the cohesion of pyrogallol through the formation of pyrogallol-pyrogallol covalent bonds is of great significance for the preparation of bulk hydrogels.This thesis is mainly inspired by the adhesion mechanism of phenols in plants,by introducing phenolic substances containing polyphenolic hydroxyl groups into the polyacrylamide hydrogel network,giving graphene-based hydrogels excellent adhesion properties;at the same time,In order to solve the problem that hydrogels are easy to freeze at low temperature,salts are introduced to prepare low-temperature freeze-resistant adhesive hydrogels.The specific experimental contents are as follows:1)The first system: High-strength,self-adhesive conductive hydrogel(GO-B-PG-PAM)were formed by selecting phenolic small molecule pyrogallol(PG),sodium tetraborate(Borate)as the phenolic hydroxyl protective agent,followed by reinforced nano-material graphene oxide(GO),and acrylamide monomer(AM)free radical polymerization.Among them,the dynamic boronic ester bond between PG-Borate,π-πaccumulation,and the hydrogen bond in the hydrogel make the hydrogel have better self-healing properties.In addition,the phenolic hydroxyl group contained in PG also imparts excellent adhesion to the hydrogel,allowing it to adhere to the surface of different materials.GO can be used as a nanomaterial to enhance the strength of the hydrogel,and it can also increase the conductivity of the hydrogel material,so that the hydrogel can be used as a strain sensor to respond to finger movement,making this graphene-based self-adhesion conductive hydrogel has a certain potential in the field of human limb movement detection.2)The second system: At present,traditional hydrogels inevitably face the challenge of long-term use at extremely low temperatures.In this case,the hydrogel freezes as soon as the temperature drops below the freezing point of water.Under such conditions,frozen hydrogels may lose their original properties,including elasticity and electrical conductivity.Therefore,in System two,the water retention capacity of the hydrogel will affect its other properties.So conductive hydrogel with anti-freezing and moisturizing adhesion was synthesized by adding lithium chloride(Li Cl)with conductivity and anti-freezing and moisturizing properties into the aqueous solution and using PG with three phenolic hydroxyl groups,protective agent Borate,conductive enhancing nanomaterials GO and AM.The introduced hydrated ions in water of Li Cl reduce intermolecular hydrogen bonds and reduce the proportion of free water in the hydrogel network,making it difficult for hydrogel to solidify.Hydrogels exhibit excellent softness and elasticity at ambient temperatures of 25 ℃ and-18 ℃.The hydrogel can be used normally in the temperature range of-20 ℃～45 ℃,and after being placed at room temperature for 7 days,the percentage of water loss is less than50%,showing good moisture retention and environmental stability.The phenolic hydroxyl group in PG also makes the hydrogels adhesive,allowing them to adhere to the surface of different materials.This expands the range of applications of hydrogels as strain sensors,making them more advantageous for use in extreme environments.