Construction And Multifunctional Applications Of Ion-Based Polymer Conductive Gels

With the rapid development of bioelectronics and flexible electronic products,various flexible electrical materials have attracted extensive attention owing to their widespread applications in wearable devices,electronic skin or artificial muscle,retractable transistors,health medicine,energy storage and conversion.Ionic conductive gels,as typical smart materials with flexibility,imitating human ionic conductivity and good biocompatibility,is desired to become the carriers of the next generation of flexible electronic devices.However,the chemical crosslinked ionic conductive gels have the defects of mechanical brittleness,poor ionic conductivity and single function.To balance the comprehensive demands about robust mechanical properties,high conductivity,multiple intelligent response and environmental tolerance of ionic gels is still a great challenge.Based on the research niche mentioned above,this paper has introduced a variety of rational strategies toward developing ionic conductive gels with strong mechanical properties,excellent ionic conductivity,multi-function response,antifreeze,water and alkali soaking.These gels have been subsequently applied to multi-functional sensors,motion monitoring equipment,health detection platform,quasi-solid-state battery,tunable electromagnetic wave absorption and shielding,and other fields.The details are as follows:（1）Sulfonated beet methacrylethyl（SBMA）and acrylic acid（AA）were used as ionic monomer,polyethylene glycol diacrylate（PEGDA-1000）and Al³⁺as chemical crosslinker and physical crosslinker,respectively.A double crosslinked ionic conductive hydrogel（DC-Sx Ay Alz）was constructed by one-step process of in-situ free radical copolymerization.Combining the reversible upper critical solution temperature（UCST）behavior,the DC-Sx Ay Alz temperature sensor can realize the visualization of ambient temperature to digital intelligent sensing.In addition,due to the dual crosslinking mechanism and the synergistic action of various conductive components of polymers and inorganic salt,DC-Sx Ay Alz shown strong mechanical properties and excellent conductivity.Therefore,it had been developed into effective strain-resistance sensor,pressure-capacitance sensor,motion monitoring equipment and electrocardiogram（ECG）monitoring platform,showing its application prospect in the fields of intelligent sensing and health monitoring.（2）On the basis of the above work,through the reasonable adjustment of monomer ratio and concentration of Al³⁺,and removal of chemical crosslinker,by means of multiple electrostatic interactions and coordination effects,a supermolecule conductive ion-based hydrogel（SC-Sx Ay Alz）with excellent tensile properties（1500%）,high strength（110k Pa）,high conductivity（～2.5 S/m）,self-healing and remolding was constructed by one-step method.Combined with density functional theory（DFT）and noncovalent interaction（NCI）,the gelation driving force of SC-Sx Ay Alz was quantitatively calculated.In addition,the functional relationship of ionic gel as strain resistance sensor under small strain and large strain was explained by fitting corresponding to variable sensing data and formulae derivation.It was noteworthy that the reconstructed SC-Sx Ay Alz retained the electrical conductivity,intelligent sensing and health monitoring of the original SC-Sx Ay Alz,indicating that the supramolecular conductive hydrogel constructed by full-physical crosslinked can realize the recycling of flexible electronic devices.（3）Combined with the construction method of ion-based supramolecular conductive hydrogel and the characteristics of secondary crosslinking of Al³⁺promoted by immersion,an ion-based polyelectrolyte hydrogel（SE-Sx Ay Alz）was constructed.SE-Sx Ay Alz shown excellent comprehensive mechanical properties,such as tensile strength 450 k Pa,fracture energy 719 k J/m³,compressive strength 22.3 MPa.The apparent activation energy of polyelectrolyte hydrogel was calculated by the time-temperature equivalence principle and Arrhenius equation.In addition,SE-Sx Ay Alz had the characteristics of water-resistance soaking,and can realize intelligent sensing without encapsulation underwater.Therefore,it can promote the development and application of next generation of water immersion high strength and high toughness ionic hydrogel sensors.（4）PAM/Laponite（PAM/Laponite）nanocomposite（NC）hydrogel was prepared by in-situ free radical polymerization.Then,the PAM/Laponite NC hydrogel was immersed in the electrolyte of 6 M KOH+0.2 M Zn（Ac）₂,and the full-ionic type of PAA-M/Laponite hydrogel was constructed by hydrolysis reaction of PAM,which was resistant to strong alkali,ultra-high conductivity（392.1 m S/cm）and antifreezing（freezing point at-55.8℃）.In addition,the application of PAA-M/Laponite NC hydrogel as solid electrolyte in quasi-solid zinc-air battery was explored.It exhibited excellent room temperature(2 m A cm^-2current density,charge/discharge 192 h and power density 207.6 m W cm^-2)and-40℃(2 m A cm^-2 current density,102 h,over 500 cycles)cycle charge/discharge performance.Meanwhile,the full-ionic NC polyelectrolyte hydrogel constructed by the two-step method had good universality and can be applied to monomers,such as HEMA,DEA and NIPAN.Therefore,the work has provided a new idea for designing solid electrolyte with safety,low-cost,flexibility,and ultra-high conductivity.（5）NC ionic gel with ionic conductivity and tunable absorbing properties was prepared by UV irradiation and in-situ polymerization.Among them,the ionic liquid（1-butyl-3-methylimidazole trifluoromethane sulfonate,[Bmim]TFSI）was used as disperser,intercalation agent,and solvent,N,N-dimethylacrylamide（DMAA）and PEGDA-1000 were used as monomer and chemical crosslinking agent respectively,and silicon nitride modified reduced graphene oxide（RGO-Si N）was used as effective absorbing component.Moreover,we explored the reason why RGO-Si N effectively regulated the absorbing properties of ionic gel,and analyzed the reversible regulation mechanism of the simple tensile-recovery process on wrinkled-like structure of the ionic gel.In addition,the tunable absorption mechanism of NC ionic gel was mainly due to the interaction between the intrinsic dielectric attenuation of RGO-Si N nanoparticles and the multiple scattering of the wrinkled-like network structure.