Preparation And Application Of Metal Salt-Based Deep Eutectic Solvents For Constructing Functional Ionic Gels

With the rapid development of flexible wearable electronic devices,flexible wearable electronic devices have shown a wide range of application scenarios in sports monitoring,medical monitoring,artificial intelligence,energy storage devices and other fields,indicating that the application of sensors as a direct product of wearable electronic devices is also attracting attention,where conductive elastomers play an increasingly important role with the development of modern technology.Most finished products for flexible wearable sensors are currently based on hydrogels or polymer elastomers,but their harsh storage conditions,single application area and lack of functionality are limiting the development of wearable flexible sensing electronics.Ionic gels have been used as a soft material for long-term storage and versatility in the fabrication of various flexible wearable sensor devices.However,most of the ionic gels that have been developed have a single function and are very limited in terms of application areas and conditions,so there is an urgent need to develop multifunctional,easy-to-store ionic gels to meet the market demand for flexible sensor devices.In this thesis,two ionic gels with different functions have been designed and prepared using a metal-based deep eutectic solvent with high heat resistance,stability and conductivity as the solvent,and assembled into flexible strain sensors for application.The main studies are as follows.Firstly,acrylic acid（AA）has been used as the monomer and the gel backbone has been polymerised to form polypyrrole（PPy）with photothermal conversion responsiveness.Due to the insoluble nature of polypyrrole,a deep eutectic solvent（DES）formed by ethylene glycol（EG）and ferric chloride（Fe Cl₃）will be used as a solvent,where the Fe Cl₃ in the DES also provides oxidation to polymerise the pyrrole（Py）.In this experiment,the effect of different ratios of DES and PAA on the performance of the gel has been investigated,and then the best ratio for application to the sensor was selected and tested accordingly.With DES and PPy as conductive fillers providing the main electrical conductivity of the gel,this ionic gel has excellent electrical conductivity,plasticity,good self-healing ability,wide temperature range of use and photothermal conversion capability.Alternatively,DES formed using zinc chloride and acrylic acid,wherein the hydrogen bond donor AA in the DES polymerises as the backbone of the gel,while zinc chloride（Zn Cl₂）enables the sodium alginate solution to be cross-linked into the gel,introducing the sodium alginate solution as the second network of the gel,forming a double network ionic gel.The presence of two gel networks improves the mechanical strength of the ionic gel and the gel has good fatigue resistance.The excellent ionic conductivity and mechanical properties of this ionic gel provide a good basis for application to flexible sensor devices.