| Amphiphiles can be assembled into micelles,vesicles,liquid crystals,nanofibers,and other abundant ordered aggregates in water,organic solvents or ionic liquids.The design of functional amphiphiles and the exploration of noncovalent interactions in the assemblies will be conducive to understand the biological assembly mechanism,prepare novel multi-functional materials,and promote the development of chemistry and related fieldsThe ordered aggregates constructed by imidazolium ionic liquids(ILs)not only introduce the unique physicochemical properties of ILs,but also provide the system with abundant noncovalent forces such as electrostatic interaction,hydrogen bonding,and ?-? stacking.In order to explore novel assembly methods and obtain multi-morphological and multi-functional assembly materials,the following methods can be improved.On the one hand,imidazole can be structurally modified or functional groups can be introduced into the hydrophilic headgroup,hydrophobic tail and counterion of the amphiphiles based on the excellent designability of ILs.On the other hand,organic-inorganic co-assembly constructed by noncovalent interactions can flexibly and effectively introduce the characteristics and functions of inorganic materials.In addition,the preparation of small molecular gels based on amphiphiles with simple and strong designability,is easy to obtain intelligent soft materials that respond to stimuli such as light,temperature and pH.It is conducive to expanding the application of the assembly and exploring the relationship between structure and functionIn this article,a series of functional imidazolium amphiphiles have been designed and synthesized.The morphologies of assemblies were regulated by multiple noncovalent interactions,to achieve responsive and functional controllable assembly.The main research work was divided into the following six parts:1.Azobenzene compounds have high efficiency and reversible trans-cis photoisomerization.Due to its strong hydrophobicity,researchers often use it as an additive to aggregate or synthesize the amphiphile with azobenzene group in the hydrophobic tail.Surface active ionic liquid[C14mimAzo]Br with azobenzene located in the headgroup was designed.The aggregation behavior in aqueous solution was studied in detail.The introduction of azobenzene increases the hydrophobicity,and reduces electrostatic repulsion of headgroup.Therefore,it can be assembled into vesicles without additives.The results of 1H NMR and UV-vis absorption spectra showed that curved cis isomer of[C14mimAzo]Br was formed after UV illumination,which causes the burst of vesicles due to the unfavorable accumulation of molecules.Density functional theory(DFT)calculation further shows that trans-[C14mimAzo]Br and H2O have smaller interaction energy,which is more conducive to the formation of aggregates.2.Cationic poly(ionic liquid)([PMAzoVIm]Br]and polyacrylic acid(PAA)have been used to fabricate photo and humidity responsive poly(ionic liquid)(PIL)porous membrane by a simple and template-free phase separation method.Since azobenzene were introduced into the branched chains of PILs,the cis-isomer produced by UV irradiation changes the volume of complex and the steric hindrance within molecules,thus changing the porous structure of membrane.The pores can be switched "on" and"off" through humidity stimulus.FTIR,SAXS,and UV-vis adsorption spectra were performed to investigate the mechanism of porous formation and structure changes.Extremely high swelling and water uptake ratios and charged character endow the membrane excellent selective adsorption capability for cationic dye methylene blue.3.Supramolecular ionogels were prepared in protic IL ethylammonium nitrate(EAN)through host-guest interaction between ?-cyclodextrin(?-CD)and zwitterionic liquid(MIPS-LiTFSI).19F NMR and 2D ROESY 'H NMR have been used to prove that only TFSI-is involved in the complexation.Host-guest interaction between ?-CD and TFSI-,electrostatic interaction between imidazole cation and TFSI-anion and intermolecular hydrogen bonding between three compounds contribute to the formation of supramolecular ionogel.Ionogels with different mechanical properties and thermal stability can be obtained by adjusting the molar ratio between ?-CD and MIPS-LiTFSI.The selection of EAN,dissociation of zwitterions to lithium salts,encapsulation of TFSI-by ?-CD,and "channel type" structural(3-CD improve the conductivity of ionogels.4.Based on the above work,we designed and synthesized an asymmetric Gemini type zwitterionic liquid(AzoIPS-LiTFSI).Low molecular weight supramolecular hydrogels were prepared with azobenzene and TFSI-as two guest molecules,which have different mechanisms of action with ?-CD.Reversible gel-sol transitions were triggered by light and temperature.The binding stoichiometry and mode of inclusion in the complex,mainly noncovalent interactions in the hydrogel,photo-and thermo-responsive mechanisms were studied in detail.Interestingly,the ?-CD can be photo-manipulated to shuttle along the guest molecule.The value of conductivity can be reversibly switched along with the gel-sol transition,which has potential application in electrical sensor materials.5.The organic-inorganic co-assembly method based on amphiphiles and polyoxometalates(POMs)combines the diversity of organic assemblies and the versatility of inorganic materials,which can be used to prepare assembly materials with excellent properties.POMs are selected to be chemically modified or assembled as the anti-ion of cationic amphiphiles,and the prepared materials are usually insoluble in water.To explore novel and simple assembly methods:(1)We have prepared supramolecular hydrogels with crystalline and amorphous networks by co-assembling zwitterionic amphiphile C16IPS with phosphotungstic acid(HPW)in an organic-inorganic way.Since the anions and cations of zwitterions are connected by covalent bonds,electrostatic attraction and repulsion exist simultaneously with the charge delocalized POMs.By balancing the rigidity and flexibility of the organic-inorganic complexes,diverse aggregates(nanofiber bundles,branched nanofibers,cross-weave wormlike micelles,parallel-aligned wormlike micelles,unilamellar vesicles,and disordered wormlike micelles)were obtained.Given the versatile applications of hydrogels in biological systems and materials science,these findings may highlight the potential of organic-inorganic binary supramolecular hydrogelators and fill in the blank between kinetic and thermodynamic controlled gelation processes.(2)To comprehensively investigate the noncovalent interactions in the system,zwitterionic amphiphiles with different cations C161PS and C16bIPS were selected and respectively assembled with HSiW.Hydrogen bonding between the oxygen atoms of HSiW and the protons on C-2 of the imidazolium rings as well as steric effect significantly influence the morphology and rheological property of hydrogel.Interestingly,cross-linked wormlike micelles in parallel,vertical and tilted distribution were obtained with different C16bIPS-to-HSiW molar ratios.In addition,these aggregates were further stacked into hexagonal phases on a large scale.Hence,deep insights into the relationship among the structure of zwitterionic amphiphile,self assembled architecture and the mechanical property of POM-based hydrogel were disclosed.6.Based on the above work,injectable hydrogels with excellent luminescent properties were obtained by co-assembly with POM containing europium(EuW10)and zwitterionic amphiphile C20IPS.Hydrogels with different rheological and luminous properties can be manipulated by adjusting the molar ratios of C20IPS and EuW10.Interestingly,two sets of linear correlation curves between the luminescence intensity and temperature accompanying the thermal responsive gel-sol transition was observed.In addition,acid/base gas can significantly affect the luminescence characteristics of hydrogels,which is conducive to the preparation of luminescent soft materials with multiple stimulus responses. |
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