Preparation Of Zwitterionic Gel Electrolyte And Its Application In Flexible Electronic Devices

Bionic electronic skin has a wide range of applications in wearable devices,artificial prostheses,soft robots and other fields.Bionic electronic skin can convert external stimuli into electrical signals to achieve the purpose of imitating the function of human skin.As a flexible sensor,electronic skin generally has high conductivity,self-healing properties,and good environmental stability,and can adapt to various environmental requirements and respond quickly and reliably to external stimuli.In this paper,the zwitterionic materials(3-(Methacryloylamino)propyl)dimethyl(3-thiopropyl)ammonium hydroxide inner salt(PDP)and acrylic acid(AA)are used as monomers.In situ copolymerization to obtain zwitterionic gel electrolyte with good performance.Due to the presence of zwitterions,the polymer chains have both positive and negative charges.Therefore,the polymer chains can be cross-linked through electrostatic interactions,and can also be closely combined with water molecules through hydration.In this paper,by adjusting the concentration and ratio of the two monomers of polymerizable zwitterion and acrylic acid,the influence on the mechanical properties,electrochemical properties,self-healing properties,freezing resistance and sensing properties of the gel electrolyte is explored.Finally,the zwitterionic hydrogel electrolyte prepared under the optimal conditions is selected as the basic element of the electronic skin,which makes the resulting device have excellent mechanical properties,including good recovery,great stretch-ability,self-repair and adhesion.At the same time,this article uses the characteristics of the ionic conductivity of the gel electrolyte to change with temperature and strain to prepare electronic skin devices with multiple stimulus-response mechanisms.Finally,in order to solve the problem of poor environmental stability and narrow application temperature range of the hydrogel electrolyte,this paper prepared an ion gel with excellent environmental stability and an antifreeze hydrogel with a wide operating temperature range,based on the flexible electronics prepared by it.The device can be used for a long time in a low temperature environment and maintain excellent performance.The main research results are as follows:(1)In this study,a physically cross-linked supramolecular hydrogel P(AA-co-PDP)was successfully prepared by the one-step thermal polymerization method by introducing AA on the basis of PDP monomer,in which PDP amphiphilic molecules provide ion transport.The channel increases the ion transmission rate,and the addition of AA greatly improves the mechanical properties of the hydrogel,which can be stretched up to about 30 times.Then,by adjusting the concentration of the lithium chloride solution,a zwitterionic hydrogel electrolyte with excellent electrical conductivity and mechanical properties was successfully prepared.The electrical conductivity of the gel electrolyte was 1.6 S/m.Finally,the zwitterionic gel electrolyte was assembled into a wearable flexible strain sensor to detect pressure,stretch,temperature and various human activities.The device showed rapid response during the detection process.(2)Although the zwitterionic hydrogel electrolyte has excellent mechanical properties,electrical conductivity and self-healing properties,its environmental stability is limited.Aiming at this problem,in this study,ionic gels were prepared by photopolymerization of ionic liquids with excellent electrochemical stability and thermal stability and PDP monomers.By adjusting the monomer concentration and monomer ratio of the ion gel,an ion gel with a wide range of mechanical properties is obtained.The fracture strain range of the ion gel is 900%-10000%,and the ion conductivity is0.432 S/m.It also has good environmental stability,and can still maintain its mechanical properties and electrical conductivity at low temperatures.The application temperature range of strain sensors based on ionic gels is very wide,and various human activities can be sensitively detected at different application temperatures.(3)Although ionic gels have excellent mechanical properties and a wide range of operating temperatures,ionic liquids are generally toxic.Therefore,in this study,a non-toxic,green antifreeze zwitterionic hydrogel was prepared by adjusting the water content of the zwitterionic hydrogel.When the water molecules in the hydrogel are all tightly bound by the positive and negative charges in the polymer chain,the hydrogel will have excellent frost resistance.When the molar ratio of amphiphilic molecules to water is 1:6,the prepared hydrogel remains unfrozen at-40°C.At-30℃,the hydrogel electrolyte has good conductivity and flexibility.The supercapacitor prepared based on the antifreeze zwitterionic hydrogel electrolyte still has good electrochemical performance at-20°C.The frost resistance of hydrogels by adjusting the water content has not been studied.In this study,a new preparation method was adopted to realize the frost resistance of hydrogels,which made up for the shortcomings of conventional hydrogels.