Preparation And Properties Of Chitosan/Polyacrylic Acid Adhesive Selfhealing Hydrogels

Hydrogels,a class of flexible materials with 3D network structures that retain high water content,have been used in drug delivery,wound dressings,flexible electronic devices,and sensors due to their adjustable physical and chemical properties and inherent similarity to biological materials.Researchers have found that the introduction of conductive substances into hydrogel systems not only improves the conductivity,but in some cases also enhances the mechanical properties,so the development and study of conductive hydrogel flexible sensors has gained the attention of scholars in recent years.However,the developed hydrogels are often limited in their applications due to their simple nature.Based on this,a multifunctional hydrogel sensor that combines excellent self-adhesive,conductive,mechanical properties and self-healing properties is constructed in this paper.The details of the work are as follows.（1）A multifunctional hydrogel sensor was successfully constructed using chitosan（CS）,2-acrylamide-2-methylpropanesulfonic acid（AMPS）,acrylic acid（AA）solution and Fe³⁺.The formation mechanism and performance study of this hydrogel were investigated.Chitosan is an alkaline polysaccharide and can only be dissolved in acidic solutions.The introduction of AMPS into the hydrogel system further dissolved the chitosan,and electrostatic interactions occurred,enhancing the mechanical properties.The fracture strength of the hydrogel was measured to be 356.81 k Pa,and the fracture strain also reached 1145%.Meanwhile,AMPS was deprotonated by the sulfonic acid group to shed H+,which promoted the ionic activity inside the hydrogel and enhanced the electrical conductivity of the hydrogel.In addition,the hydrogel is highly sensitive to both large and small strain and velocity response.And there is no significant decay of the response signal in successive tensile cycles,indicating that the hydrogel has stable and reproducible responsiveness.（2）To further explore the performance characteristics of the hydrogel,the chitosan molecule contains a large number of hydroxyl and amino groups,the incorporation of functional groups of AMPS and Fe³⁺,the synergistic metal complexation of chemical cross-linking and electrostatic interactions make the hydrogel exhibit a wide range of adhesion in air and under water on the surface of materials such as aluminum,rubber,plastic,glass and pigskin.In particular,the hydrogel can achieve peel strengths of 276.05N/m and 421.97 k Pa for pigskin in air and water,respectively.the mechanical strength of the hydrogel before and after healing was tested and its healing efficiency reached 68%.The hydrogel,as a strain sensor,not only transforms human movements into changes in electrical signals,but is also capable of detecting signals in minute movements such as blinking and nodding.In this thesis,a multifunctional hydrogel was prepared by a one-pot method to use it as a wearable strain sensor.Since the hydrogel is self-adhesive,the sensor adheres tightly to the skin and does not fall off during signal detection.Therefore,this work is also expected to provide a new strategy for developing multifunctional sensors,thus expanding the promising applications of hydrogel sensors in flexible wearable devices,electronic skin,and medical monitoring.