Preparation And Properties Of Highly Stretchable Photoluminescent Ionogel

In recent years,ionogels have been widely used in gel electrolytes,electro-actuators,soft robots and wearable flexible sensors.However,traditional ionogels have poor flexibility and stretchability（<100%）,and are difficult to resist unpredictable external destructive force（such as bending,twisting,stretching,etc.）and large deformation.Meanwhile,their lack of functionality（self-healing,adhesiveness,photoluminescence,etc.）greatly limits their application.Therefore,the design and preparation of functional highly stretchable ionogel has gradually become a research focus in this field.In this paper,self-crosslinking epoxides,metal ions and dendritic macromolecules have been used as cross-linking centers to prepare photoluminescent ionogels with good flexibility and tensile properties（>1000%）,and their applications in wearable sensors and human-machine interfaces were studied.The specific research content of this paper includes the following three aspects:（1）A photoluminescent poly（ionic liquids（IL））-based Ionogel containing epoxy groups with highly stretchable and electrical conductivity has been prepared by in-situ copolymerization and cross-linking of Ionic liquids（ILs）without adding any conventional cross-linker or chromophore.Here,the ILs serves as a solvent,electrolyte,and catalyst,while the product of the ring-opening reactions acts as cross-linking center.The results reveal that these systems are typical self-catalytic systems and that the ILs anion type significantly influences the curing reaction kinetics.These ionogels exhibit excellent stretchability（>1200%）,high ionic conductivity（>1 m S/cm）,and good temperature tolerance（-40 to 200^oC）.Surprisingly,the special cross-linking structures make the ionogels show typical aggregation-induced luminescence behavior and possess tunable photoluminescence properties.Moreover,ionogel-based strain sensors exhibit fast response speed,excellent temperature tolerance and stability,and can monitor various human motions.（2）Using acrylic acid（AA）as monomer and zinc dimethacrylate（ZDMA）as crosslinking agent dissolved in EMIM（Et O）₂PO₂,a self-healing and high-stretchable ionogel with both chemical cross-linking network and physical cross-linking network was prepared by one-step photoinitiated polymerization.The ionogel has good transparency（95%transmittance）,stretchability（2770%）and excellent self-healing properties（69 s）.More importantly,due to hydrogen bond interactions within and between PAA chains and dynamic interactions between Zn²⁺in ZDMA and-COO^-on the PAA chain,the ester groups on the polymer chain are aggregated,leading to aggregation-induced luminescence（AIE）behavior of the ionogel.At the same time,Ionogel can also be used as a good strain sensor to monitor the size and deformation movement of the human body due to its excellent tensile and self-healing properties.（3）An ionogel with chemical cross-linking,hydrogen bond interaction,ion-dipole interaction and dipole-dipole interaction was prepared by means of hyperbranched polymer（HP-A）covalent-cross-linked poly（zwitterionic ionic liquid）-co-poly（acrylic acid）.Due to the multiple interactions between the polymer network,an ultra-stretchable（>10000%）,ultra-strong adhesive（6.8 MPa）,ultra-fast self-healable（10 s）,high thermally stable（-60 to250°C）photoluminescent ionogel has been designed.At the same time,we mimicked the sensations of the human skin by developing multifunctional stretchable ionic skin（I-Skin）,which showed promising potential in wearable sensors and human-machine interfaces（HMI）.The excellent performance of the ionogel-based high-stretchable strain sensor and the triboelectric nanogenerator（TENG）-based self-powered touch sensor is further demonstrated over a wide temperature range（-40 to 150°C）.More importantly,ionogel-based I-Skin can work as an HMI for human gesture recognition and real-time wireless control of robots under extreme vacuum conditions and can also self-heal immediately along with function recovery after mechanical damage.