The Creation And Application Of Calix[4] Arene-based Dynamic Covalent Bond Gel

As an important soft material,gels play a significant role in the fields of sensors,soft robots,drug delivery and template synthesis.However,in these practical applications,the gels are required to present both stability and multiple stimuli responsiveness,which raises new claim for the design and preparation of such materials.Dynamic covalent gels are constructed by dynamic reversible covalent bonds or dynamic reversible reactions,including imines,acylhydrazones,boronate ester and disulfide.Therefore,these gels could present sol-gel phase transition and volume phase transition behaviors responding to chemical and/or physical stimuli.Moreover,the stability of the gels may be improved due to the dynamic covalent nature of the network structure.In addition,the introduction of macrocycles,such as calixarene,into the dynamic covalent gels can further enrich their stimuli responsiveness and conformational variability.This thesis focuses on the construction of novel dynamic covalent gel with multiple structure and functions by combining the macrocyclic ring with dynamic covalent bonds.In the first work,the lower edge of the calix[4]arene derivative modified by four hydrazide groups and five linear PEG-CHOs with different molecular weights terminated by benzaldehyde group were designed and synthesized.A dynamic covalent bond gel could be constructed with a dynamic acylhydrazone bond by using these two molecules.It was found that gel G-0 formed by the compounds of CTH and PEG4208 in a mixed solvents of EtOH/H2O=3/1(v/v)showed anti-compression ability with a high strength of 6.41 MPa and the fracture strain of 88.21%.The gel could self-heal,which could be accelerated by the addition of aniline as the catalyst.Moreover,it underwent a sol-gel phase transition under the stimuli of pH and/or temperature.To the best of our knowledge,this is the first case of dynamic covalent bond gel with high mechanical strength,cutting resistance,fatigue resistance,stimuli responsiveness and self-healing properties,which is promising for applications in flexible electronics,artificial skin,flexible sensors and flexible batteries.In the second work,a dynamic covalent bond gel was prepared with the calix[4]arene derivative CTBA modified by four phenylboronic acids and PVA through the dynamic boronate ester bonds.The ionic liquid gel could be constructed through solvent exchange process from the gel prepared in a mixed solvent of H2O/EtOH=9/1.As-obtained ionic liquid gel exhibited excellent self-healing,multiple stimuli responsiveness and fatigue resistance properties.In addition,the ionic liquid gel was nearly complete transparent to visible light.Therefore,it was used for the preparation of novel soft optical device,which had basically satisfied the basic requirement for conventional glass optical instrument.More interestingly,as-prepared soft optical device showed self-healing and recyclable behaviors,saving the cost and reducing pollutants to achieve green environmental protection.Hence,ionic liquid gel is expected to be applied in the fields of flexible screens and soft optics.