Preparation And Application Of Self-healing Supramolecular Ionogels

Formation of supramolecular ionic liquid(IL)gels(ionogels)induced by low-molecular-mass gelators(LMMGs)is an efficient strategy to confine ILs,and the negligible influence of LMMGs on the intrinsic properties of ILs makes ionogels ideal functional materials.Furthermore,the stimuli-responsive and self-healing characters of the supramolecular gel can be utilized for the potential development of smart materials.However,the poor mechanical properties of supramolecular ionogels reported so far limit their practical applications.Herein,a series of efficient D-gluconic acetal-based gelators(Gn,PG16,and B8)were investigated,which can harden a wide variety of ILs at low concentrations.It was shown that both alkyl chain length and the number of hydrogen bonding sites of a certain gelator,as well as the nature of the IL anion,significantly influenced the gelation abilities.The resulting ionogels were thermally reversible,and most of them were stable at room temperature.Interestingly,a PG16-based supramolecular ionogel showed rapid self-healing properties upon mechanical damage.Furthermore,the PG16-based ionogel demonstrated unprecedented performances including the favorable ionic conductivity,excellent mechanical strength,and enhanced viscoelasticity,which make it a great self-healing electrochemical material.The ionogel formation mechanism was proposed based on the analysis of Fourier transform infrared,¹H NMR,and X-ray diffraction,indicating that a combination of hydrogen bonding,?-?stacking,and interactions between alkyl chains was responsible for the self-assembly of gelators in ILs.Furthermore,in order to prepare a better self-healing supramolecular ionogel,a new D-gluconic acetal-based gelator(PB8)bearing a urea group in the alkyl side chain was designed.Interestingly,the balance between hydrophilicity and hydrophobicity of the molecule is achieved.Thus,PB8 could form transparent ionogels because of its excellent affinity to ILs,which exhibited appropriate mechanical strength,high viscoelasticity,and efficient self-healing properties.The presence of synergistic effects from hydrogen bonding,?-?stacking,and interactions between the urea-containing side chains was responsible for the self-assembly of gelators in ILs and the self-healing property mainly related to the side chains of PB8.Notablely,the transparent PB8-[C₄C₁C₁im][TFSI]ionogel possessed high conductivity and mechanical strength,moldable and injectable properties,and rapid and complete self-healing characteristics(complete recovery within 14 min),which showed excellent performance as a smart ionic conductor.Moreover,the self-healing PB8-based ionogels with anticorrosion properties are a remarkable lubricating material in the steel-steel contact and exhibited excellent lubricating performances.Overall,the studies on exploring the structure-property relationship of gelators for the formation of practically useful supramolecular ionogels shed light for future development of more functionalized ionogels.