Preparation Of Super Tough Ionic Conductor And Its Application In Flexible Electronic Devices

Flexible wearable electronics have broad application prospects in flexible sensing,flexible display,health care,human-computer interaction and other fields due to its advantages of high flexibility,low preparation cost,and compatibility with human body.As an important component of flexible wearable electronic devices,flexible tensile conductive materials have also attracted the attention of researchers.Compared with flexible stretchable electronic conductors,flexible stretchable ionic conductors represented by gel electrolytes have better mechanical behavior and biocompatibility.Among them,ionic conductive hydrogels have been widely used in the field of flexible wearable electronics,but because they contain a large amount of solvent water and have poor environmental stability,they are prone to failure of devices due to water loss or icing in extreme environments such as high and low temperatures.In order to improve the environmental stability of gel electrolyte,an effective method is to replace water in gel electrolyte with ionic liquid to obtain ionic gel.Benefiting from the advantages of ionic liquids such as low vapor pressure,high ionic conductivity and high electrochemical stability,ionic gel have high environmental stability.However,due to the shielding effect of ionic liquid,the cross-linking density of the polymer network in the ionic gel is reduced,resulting in the low mechanical properties of ionic gel,such as low breaking strength（<1 MPa）and low toughness(～1000 J m^-2),which makes it easy to cause failure of related devices due to fracture.In order to solve the problem of poor mechanical performance of ionic gel,this paper prepared an ionic gel with high strength,high toughness and self-healing ability through reasonable structural design.Based on this,a bionic artificial skin was assembled,which can accurately monitor physiological signals such as human movement and bioelectricity,and achieved application verification in human-computer interaction interface.Furthermore,aiming at the problem that gel electrolyte is easy to leak under the condition of large deformation,a solvent-free high strength and toughness ionic conductive elastomer was prepared through reasonable composition optimization.Compared with ionic gel,the prepared ionic conductive elastomer has better mechanical properties and working stability.Based on this,a wearable sensor with multimodal sensing ability is assembled,which realizes multi-dimensional sensing of pressure,strain,temperature,etc.Through the above work,this paper provides a possible strategy and approach for the design and synthesis of high-strength and flexible tensile ionic conductors.The main results are as follows:（1）Preparation and application of high strength and toughness ionic gel.In this study,the physical crosslinked PDP-PAA-IL supramolecular ion gel was prepared by one-step photopolymerization of the amphoteric material（3-（methacrylamido）propyl）dimethyl（3-thiopropyl）ammonium hydroxide inner salt（PDP）,acrylic acid（AA）,and ionic liquid1-ethyl-3-methylimidazole ethyl sulfate（IL）.The phase separation mechanism was introduced to construct the AA rich hard domain and the PDP/IL rich soft domain in the gel,and the high strength and high toughness ionic gel was successfully prepared under the synergistic effect of the soft and hard phases.The fracture strain range of the prepared ionic gel is about 600%-1400%,and the fracture strength range is about 0.2 MPa-33 MPa.It has high fracture energy and good self-healing performance.The wearable sensor based on this ionic gel can effectively monitor physiological signals such as human movement and bioelectricity,and has achieved application verification in human-computer interaction interface.（2）Preparation and application of high strength solvent-free ionic conductive elastomer.In this study,the amphoteric materials（3-（methacrylamido）propyl）dimethyl（3-thiopropyl）ammonium hydroxide inner salt（PDP）,acrylic acid（AA）,choline chloride（Ch Cl）were prepared by one-step photopolymerization.The hard domain rich in AA and the soft domain rich in PDP/Ch Cl were constructed in the elastomer by introducing a phase separation mechanism.The solvent-free ionic conductive elastomer with high strength and toughness was successfully prepared under the synergistic effect of soft and hard phases.The prepared ionic conductive elastomer has a fracture strain range of about 180%-1550%,a fracture strength range of about 7.5 MPa-21.5 MPa,and a high fracture energy.And because PDP has formed an ionic conductive channel inside,it has a high ionic conductivity of about2.3*10^-4S m^-1.Based on this,a wearable sensor with multi-mode sensing capability is assembled to realize multi-dimensional sensing of pressure,strain,temperature,etc.