Preparation And Properties Of Flexible Conductive Materials Based On Polymerizable Deep Eutectic Solvents

Flexible conductive elastomers are a class of stretchable soft materials with electrical conductivity.Due to their lightweight and good flexibility,they have attracted considerable attention in the fields of electronic skin,soft robots,and human health monitoring.As a new generation of ionic liquids,deep eutectic solvents have the advantages of environmental protection,simple preparation,and low cost,making them have broad development prospects in the field of preparing flexible conductive elastomers.However,at present,the application of deep eutectic solvents is mostly focused on the dissolution and separation of biomacromolecules,while the development of deep eutectic solvents in polymer gel has received little attention.Therefore,this paper is committed to preparing high-performance eutectic gel with deep eutectic solvent and exploring its application in flexible sensors,and has carried out the following work:1.In order to solve the problem of poor mechanical properties of deep eutectic gels,a double network composite gel was prepared by combining hydrogel with deep eutectic solvent.The composite gel overcomes the defects of hydrogel,such as easy loss of water,freezing at low temperature and poor mechanical properties of deep eutectic gel.We filled the porous structure of polyacrylamide hydrogel(PAAM)with deep eutectic solvent(DES).Through free radical polymerization of deep eutectic solvent in the porous structure of hydrogel,a double network composite gel with excellent mechanical properties and low temperature resistance was formed.By adjusting the mass ratio of polyacrylamide hydrogel to deep eutectic solvent,the electrical and mechanical properties of the composite gel can be flexibly adjusted.Due to the large number of amide and carboxyl functional groups in the double network composite gel,strong hydrogen bond interaction can be formed,and the composite gel has excellent mechanical properties(strain up to 1373%,stress up to 3.14 MPa).In addition,choline chloride in deep eutectic solvent gives the composite gel good conductivity(～0.21 m S/cm).The gel resists low temperatures(-20℃)because the water in the composite gel is replaced by a deep eutectic solvent.This dual network composite gel opens up a new method for preparing organic transparent conducting elastomers.2.In this paper,deep eutectic gels(-25°C)and high temperatures(60°C)were prepared by introducing glycol/choline chloride deep eutectic solvent into acrylamide/choline chloride deep eutectic solvent as a "hydrogen bond crosslinking density regulator".By introducing 2-acrylamide-2-methyl-1-propane sulfonic acid into the gel,the adhesive capacity of the gel on the copper plate can reach 90 k Pa and show good reusability.It has good mechanical properties(up to 2300% strain and 0.21 MPa stress)due to complex hydrogen bond interactions in the gel.Because of the presence of choline chloride,the ionic conductivity of the gel can reach 0.22 m S/cm.In addition,because the polymerization reaction is triggered quickly under UV light,this allows us to print any shape of gel on any surface.This kind of deep eutectic gel with self-adhesion,inherent conductivity,excellent mechanical properties and extreme temperature resistance has a wide range of applications in the field of motion sensors.3.In this paper,a deep eutectic solvent(DESD)with hydrogen bond acceptor as polymerizable monomer was proposed for the first time,and a traditional deep eutectic solvent(DESA)with hydrogen bond donor as the first network.Polyvinyl alcohol(PVA)was introduced as the second network to prepare double-network eutectic gel.DESD can promote the crystallization of polyvinyl alcohol,and DESA can inhibit the crystallization of polyvinyl alcohol.By controlling the proportion of two deep eutectic solvents,flexible regulation of the crystallization of polyvinyl alcohol can be achieved.The crystalline domain formed by polyvinyl alcohol acts as a physical crosslinking point to enhance the mechanical properties of the gel(elongation at break up to 1500%,fracture stress up to 4 MPa).And the deep eutectic solvent gives the gel good ionic conductivity(conductivity up to 0.9 m S/cm).This eutectic gel is completely cross-linked in a non-covalent form and therefore has an excellent self-healing and recyclable capability.This eutectic gel with excellent tensile properties,ionic conductivity,selfhealing ability and recyclability has a broad development prospect in the field of wearable electronic devices.