Preparation And Properties Of Ion-conducting Soft Materials With Self-reporting And Self-healing Functions

Ion-conducting soft materials are a kind of conductive materials which rely on the directional migration of ions for current transmission.They are particularly suitable for the applications in wearable devices,human-computer interactive touch pads and energy storage due to their advantages of satisfactory electrical conductivity and flexibility,mechanical properties matching the human body,and working mechanisms consistent with the biological systems.However,the ion-conducting soft materials are relatively soft and are subjected to repeated wear,cutting or piercing of sharp objects and other damage during use.The accumulation of these damages will lead to the eventual material failure.Inspired by biological systems,scientists have developed a variety of self-healing materials and damage-reporting materials.Intrinsic self-healing materials have attracted the attention of researchers due to their advantages such as simple preparation processes and the ability to achieve multiple healing at the same damaged sites.However,the reversibility of reversible covalent bonds and noncovalent bonds endows materials with the healing ability while causing them to lose kinetic stability.Therefore,it becomes a challenge to balance the kinetic stability and intrinsic healing ability of materials.When the material is damaged,the occurrence of damage behavior needs to be observed in time before healing,so it is also necessary to develop the damage selfreporting materials.Among the damage self-reporting materials studied so far,the discoloration-based damage self-reporting materials cannot afford the task of self-reporting in the dark environment;the fluorescence-based damage self-reporting materials need the help of external ultraviolet light source,and ultraviolet light irradiation will accelerate the aging of materials.Therefore,it is also a challenge to realize the self-reporting and rapid localization of damage in the dark conditions.Based on the above-mentioned problems,this thesis reconciles the contradiction between the kinetic stability and self-healing ability of materials by employing chemical fuels to temporarily regulate the intrinsic healing ability of ion-conducting soft materials on the one hand;on the other hand,the reactive components are introduced into ionconducting soft materials or using their own electrical conductivity to realize the self-reporting and rapid localization of damage by means of optical/electrical reporting methods.The main research contents are as follows:(1)Transient chemical activation of covalent bonds for healing of kinetically stable and multifunctional organohydrogelsWe present a new strategy to regulate the intrinsic healing ability of kinetically stable organohydrogels by using artificial reaction cycle.When the kinetically stable gels were damaged,acidic buffer solution(chemical fuels)was applied to the fractured site.By combining the double decomposition reaction with the energy dissipation process,the simplest artificial reaction cycle was constructed to induce a transient out-of-equilibrium states at the damage site,thus enabling the healing of kinetically stable organohydrogels based on acylhydrazone bonds.In addition to balancing kinetic stability and healing ability,the use of artificial reaction cycle also makes the material have high tolerance to harsh conditions such as organic solvents(glycol),high ionic strength(2 M NaCl),and high and low temperatures(-80～120 ℃).The organohydrogels maintain mechanical flexibility and conductivity even at-40℃ and enable recycle.The integration of artificial reaction cycle into polymeric materials could provide a new idea for the development of manufacturing next-generation electronic devices.(2)Self-reporting of damage in underwater hierarchical ionic skins via cascade reactionregulated chemiluminescenceWe present a new strategy based on a chemiluminescence approach to report damage for underwater hierarchical ionic skins(HI-skin).The chemiluminescence-based damage selfreporting method is regulated by a cascade reaction.When HI-skins were mechanically damaged underwater,the pre-embedded calcium peroxide particles were exposed to water environments and reacted with water molecules to produce hydrogen peroxide,and futher activating the peroxyoxalate chemiluminescence reaction to report the damage.The chemiluminescence was up to 12 h and the wavelength could be tuned.In addition,the HI-skin also exhibited high mechanical healing efficiency(93%),excellent stretchability(1600%),impressive ionic conductivity(1.7×10-4 S/cm)and durable strain sensing performance(1000 uninterrupted strain cycles),which was expected to be used as a new ionic skin for underwater wearable devices.(3)Supramolecular ionogels for damage localization of underwater infrastructuresIn the previous work,damage self-reporting of underwater materials was achieved using chemiluminescence approach.However,the preparation process of the damage self-reporting materials based on this method is tedious.Based on the problem,a supramolecular ionogel with excellent mechanical properties,high mechanical healing efficiency(83%),underwater adhesion property,high ionic conductivity(1.1×10-4 S/cm),and solvent resistance was designed.The ionogels can be prepared by the polymerization of fluorine-containing monomers with hydroxyl-containing monomers in ionic liquids via photoinitiation based on hydrogen bonds and ion-dipole interactions.The preparation method is simple and fast.With excellent adhesion ability and ionic conductivity,the ionogels can be adhered between two copper electrodes and attached to the surface of the underwater infrastructures for damage localization using resistance measurements.In addition,the ionogels can be used as an ionic cable to provide an audible self-reporting through strain change.The ionogels can also be attached to human body parts for underwater communication,thus safeguarding the lives of maintenance man in the process of rescuing underwater infrastructure.The study demonstrates the feasibility of fabricating multifunctional and versatile materials using a simple polymerization method,providing a new idea for the development of damage self-reporting materials.