Development Of Supramolecular Gel-based Multifunctional Materials,Whose Stimuli-Responsiveness Is Controlled By Competitive Coordination

As a soft material, supramolecular gels are widely used in various areas of our daily life. With the increasing development of supramolecular gels, stimulus-responsive supramolecular gels as a smart material were paid more attention to by researchers. When supramolecular gels were stimulated by temperature, light, pH, ions or compounds, mechanical strength etc., the gels can produce the appropriate response, such as sol-gel transition, change in color or fluorescence. Therefore stimulus-responsive supramolecular gels have good controllability and adjustability. However, the ion stimuli-responsive supramolecular gels as a new class of sensor has importantly significance for the response to a specific ion in an aqueous system or achieving environmental testing. After years of efforts, although the stimulus-responsive supramolecular gels made great development, it is still a big challenge to design and synthesize novel smart supramolecular gels that can optically sense a given chemical stimulus with specific selectivity or multianalyte sensing and to richen the diversity of stimuli-responsive performance. In order to solve the above problems, by rationally introduced ion regulation mechanism we created a novel supramolecular gel could recognise the target ion with specificity and richen the diversity of stimuli-responsive performance.Firstly, a novel supramolecular metallogel-based anions sensor array has been developed. It is worth mentioning that this five-member sensor array?CuG, FeG, HgG, CrG and ZnG? only needs a single synthesized organogelator G1. The AIE and anions response properties of the G1 could be tuned by different metal ions. This sensor array could sense CN-, SCN-, S^2- and I- with high selectivity and sensitivity. Moreover, the G1-based metallogels?MGs? films could act as not only convenient reversible anions(CN-, SCN-, S^2-, I-) detection test kits, but also erasable security display materials.Secondly, based on the traditional stimulus-response mechanism and ion competition mechanism, we have designed and synthesised a novel vinyl-ketone-based organogelator G3 which can be self-assembled into organogel and show ions stimuli-responsive properties via a novel "keto-enol tautomerization"-based self-assembly and stimuli-response mechanism. The G3 can transform into G3' by the keto?G3?-enol?G3?? tautomerization. The organogel OG3 show strong AIE. Since the formation and stability of the OG3 is affected by the relative content of the system two isomers?G3 and G3'?, and the G3 and G3' can be controlled by the ion competitive coordination. Therefore OG3 can dual-channel sense S^2- with specific selectivity via reversible sol-gel transition and fluorescent changes. In addition, by the competitive coordination of gelator, Zn²⁺ and anions, the sol changed to the gel state and the strong brilliant blue fluorescence emerged again. Moreover, ion-responsive films based on OG3 have been developed. The OG3 and OG3+S^2- films could act as not only convenient reversible S^2- and Zn²⁺ detection test kits, but also erasable dual-channel fluorescent display materials.Thirdly, by rationally introduced various well-designed competitive binding interactions into a supramolecular gel, a twenty-two member sensor array has been successfully developed. This sensor array could sense fourteen kinds of important ions such as CN-, F-, SCN-, Hg²⁺, Pb²⁺ etc. with high selectivity and sensitivity in water solution. This sensor array need only one synthesized receptor G4. Moreover, by this method, we also obtained a series of ions response fluorescent supramolecular materials, which could act as erasable security display materials. Therefore, this is an efficient and simple way to develop sensor array as well as stimuli-response supramolecular materials.Finally, G5 was designed and synthesized and a variety of metallogels were prepared by the competitive coordination of different metal ions with the OG5. The results prove that FeG could sense H₂PO₄^- with high selectivity and sensitivity in aqueous solution. The detection limit of the fluorescence spectral change is calculated on the basis of 1.0×10-6 M. Moreover, H₂PO₄^--responsive film based on FeG have been developed. The FeG film could act as not only convenient reversible H₂PO₄^-detection test kits, but also erasable fluorescent display materials.