Stimuli-responsive Supramolecular Materials Based On Ionic Self-assembly Strategy

Recently,with the rapid development of supramolecular materials,new materials such as supramolecular gels,supramolecular sensors,supramolecular polymers and supramolecular catalysts are emerging.Thereinto,the stimuli responsive supramolecular materials have attracted the interest of researchers because of their morphologies and properties could be altered by the external conditions.Ionic self-assembly?ISA?,as one of the supramolecular assembly methods,has some advantages,such as simple operation,high product purity and avoiding complex organic synthesis steps.Therefore,it has been widely used in micro and nanoscale materials preparation.In this thesis,based on the ISA strategy,we constructed a variety of stimuli-responsive supramolecular nanomaterials,and researched their functions.It mainly includes the following four parts:Chapter 1 introduces the concept of ISA and the recent research status of it and stimuli-responsive supramolecular materials at home and abroad.Then based on this,the research ideas of this thesis have been proposed.In Chapter 2,photo-responsive supramolecular nanoscale materials were prepared by cationic azobenzene surfactants,C₂H₅-azobenzene-OC₆H₁₂-N+?CH₃?₃Br-?ETAB?,and polyoxometalates?POMs?based on the ISA strategy.?1?Supramolecular materials were prepared in aqueous solution by ETAB and Keggin type polyoxometalate?POM?.The driving forces and self-assembly mechanism of ETAB/POM complex were studied by nuclear magnetic resonance?NMR?spectroscopy,Fourier transform infrared?FTIR?spectroscopy,UV-vis absorption spectroscopy and small angle X ray scattering?SAXS?.The as-prepared supramolecular materials show obvious response to UV irradiation:the turbidity of the solution increases with the UV irradiation on a macro scale;the coral-like nanoparticles change into dispersive nanoparticles on a micro scale.?2?In the aqueous solution,the supramolecular materials were prepared by using Eu-containing polyoxometalate?Eu-POM?and ETAB.The supramolecular material was found to have better fluorescence property than Eu-POM,and show excellent responsive properties to UV light,solution pH and additional Cu2+ stimuli.The supramolecular materials have the potential in UV detection,sensor and optical storage fields.In Chapter 3,photo-responsive dumbbell-shape supra-amphiphiles were constructed by photo-responsive bola-type azobenzene surfactant Br-?CH3?3N+-C₆H₁₂O-azobenzene-OC₆H₁₂-N+?CH₃?₃Br-?BTHA?and naphthalene sulfonate isomers with different substituent position?1-NSA,2-NSA?.It was found that the substituent position of the counterions had a significant effect on the assembly process the supra-amphiphiles and the formation of the supramolecular materials.BTHA/1-NSA forms a dendrite-like nanostructure,while BTHA/2-NSA displays a rhombus-like morphology.XRD technique and quantum chemistry software?Gaussian 09 and MOPAC2016?were used to explain the assembly mechanism on the molecular level.Additionally,the two supra-amphiphiles show excellent photo-responsive properties:not only the fluorescence intensity was enhanced,but the maximum emission position shifted to some extent upon UV irradiation.Favorable light stability of the supra-amphiphiles makes them act as a fluorescence switch.In Chapter 4,supramolecular complex fabricated by surface active ionic liquids?SAILs?and Eu-POM,and their application in biology detection was investigated.?1?Gemini surface active ionic liquid,1,2-bis?3-hexadecylimidazolium-1-yl?ethane bromide([C₁₆-2-C₁₆im]Br₂),was synthesized,then Eu-POM/[C₁₆-2-C₁₆im]Br₂ supramolecular complexes modified with copper???ion were fabricated.A novel supramolecular fluorescence probe was prepared and applied to the rapid detection of hydrogen sulfide.Although the addition of copper???ions led to a slight fluorescence quenching of Eu-POM/[C₁₆-2-C₁₆im]Br₂ supramolecular nanoparticles,the modified probe still has strong fluorescent intensity.Cu²⁺-modified supramolecular sensor?CSS?showed fluorescence and UV absorption dual signals for the rapid detection of hydrogen sulfide,and represented excellent sensitivity and selectivity.We also studied the fluorescence quenching mechanism of CSS probe for hydrogen sulfide.This study is of great significance in the diagnosing of some diseases,such as Alzheimer's disease and Down syndrome.?2?Surfactant-encapsulated complexes?SECs?fabricated by amide-functionalized SAIL,[C₁₂ImCONH₂]Br,and Eu-POM.The binding ratio of the supramolecular system was confirmed by isothermal titration calorimetry.The cytotoxicity experiments showed the nanoparticles had good biocompatibility.The photoluminescence properties of the supramolecular structures were remarkably enhanced compared with Eu-POM,and exhibited good response to hydrogen peroxide.It is expected to be applied to the detection of hydrogen peroxide.