| Owing to the unique size-dependent chemical and physical properties,the study of nanostructured materials has become one of the most active research fields.On the one hand,Nanoparticles as one kind of "hard materials" have been widely applied in the fields of photonics,electronics,magnetics,catalytic,etc.On the other hand Lyotropic liquid crystal(LLC)as a representative of "soft matter",pay great important role in novel functional nanostructure materials design,device hybrid materials development,biocatalysis and drug nano-controlled release.Now,the developments of nanomaterials and correlative theory rely increasingly on a variety of advanced testing methods and scientific equipments. Thereinto,small-angle X-ray scattering(SAXS)as a non-destructive and in-situ method,has become a powerful research tool in colloid dispersive systems and organized molecular assemblies.In this dissertation,SAXS is utilized to analyze the size and morphology of nanoparticles.Furthermore,it is also applied to characterize the structures of various LLC and the self-assembled form of surfactant.This dissertation consists of three main parts.In the first part,noble metal(Ag,Au)nanoparticles with different surface properties as well as core-shell shapedγ-Fe2O3@Au nanoparticles are prepared in aqueous phase.Different surfactant molecules such as cetyltrimethylammonium bromide(CTAB)and sodium oleate(SO)are selected as capping agent to fabricate positivelyly or negativelyly charged particles.Based on SAXS data,products' morphology and size distribution are characterized through many different analytical ways such as UV-visible spectrum(UV-vis),Transmission Electronic Microscopy (TEM),Fourier-transformed infrared spectroscopy(FTIR),nuclear magnetic resonance(NMR),differential scanning calorimetry(DSC)and thermal gravimetric analysis(TGA).SAXS are also adopted to investigate particles' surface properties.Compared with non-coated nanoparticles,red shifts have been observed in UV-vis absorption band for CTAB-coated and SO-coated particles.According to the Guinier curves of SAXS data,the average sizes of coated particles in the sol are larger than those measurements by TEM,where the margins are close to the coating thicknesses.Moreover,positively deviations from Porod's law occur for coating particles because of density fluctuation which derive from thermal electron movement or compositional heterogeneity within phases.Through SAXS and other measurements,CTAB-coated Ag nanoparticles,which were prepared successfully by a classical method to change silver nitrate to diamminesilver ion to avoid AgBr formation before reduction,are confirmed that CTAB molecules cap Ag core via their headgroups and form a bilayer shell on the surface of Ag clusters.It have also been proved thatγ-Fe2O3 is coated by Au shell about 13.8 nm thickness calculated from a Porod's negatively deviation curve which attribute to the interlayer within phases and the average size of core-shell shaped nanoparticles is about 50 nm.Obtained results suggest that the dispersion state of nanoparticles in the sol can be determined quickly and accurately through SAXS technique,which will provide important reference information on preparation of nanoparticles in solution as well as a quick and effective way for wet-nanomaterials characterization and analysis.In the second part of dissertation,LLC phases made of ionic surfactant is formed with the aim to systematically study the self-assembly structures of anion surfactant sodium bis(2-ethylhexyl)sulfosuccinate(AOT)with two alkyl chains and cation surfactant CTAB with single alkyl chain.Furthermore,various ionic liquids (IL)with long alkyl chain,which can be regarded as a special surfactant,are introduced to explore the blending compatibility with conventional surfactant.In the AOT/H2O lamellar phase,its structure can be tuned by surfactant concentration,temperature or adding cosurfactant.Based on SAXS data,the structural transformation from micelle to lamellar phase with increasing AOT concentration is investigated,meanwhile the arrangement of hydrocarbon chains will change from sparse to dense status and the ordering of LLC will be improved.The higher ordering of LLC will also be obtained through increasing temperature or adding short-chain alcohols in a certain range,which will result in a smaller effective area of AOT molecules in the polar/apolar interface or a larger hydrophobic volume of surfactant.However,there is an abnormal structure when the AOT concentration is 40 wt%,where the 1stscattering peak is missing because of deformed lamellar structures.Thus the structural transition in the process of ordering improvement is researched using SAXS and Dissipative Particle Dynamics(DPD)methods.It is proposed that at about 40%concentration,a defective structure,pseudo-reversed hexagonal phase,is formed to evidently decrease the water diffusivity,which might produce some mesophase property changes,such as reduction of the liquid crystalline long-range order.Unlike the AOT/H2O system,CTAB will form hexagonal structure in aqueous solution as well as lamellar phase by adding a certain concentration of 1-octanol.On the basis of detailed analysis of structural parameters,the blending compatibility between IL and CTAB is discussed.It conclude from SAXS results that[C16mim]Cl has good compatibility and consistent coordinated response for temperature with CTAB so as to from homogeneous LLC.Nevertheless,the LLC structures will break up to from micellar phase when blending[C8mim]Cl at lower concentration with CTAB for shorter alkyl chain of IL.Finally,phase separations take place in the blending system of CTAB and IL when substituting PF6- and BF4- for Cl-,where the upper phase is IL solution and the lower phase is LLC which comprises of multistructures such as lamellar,hexagonal and cubic arrays.These results will be helpful to illuminate the mechanism of ionic surfactant self-assembly and provide valuable reference for improving the ordering of LLC. Initial exploration for the blending compatibility between IL and conventional surfactant will be beneficial to understand the interaction of such amphiphilic molecules and enlarge the ILs' application in ordering structural materials.At last,LLC formed in IL named novel environmentally friendly solvent will be deeply investigated in this paper.Two typical imidazolium salts,the hydrophilic 1-butyl-3-methylimidazolium tetrafluoroborate(Bmim-BF4)and the hydrophobic 1-butyl-3-methylimidazolium hexafluorophosphate(Bmim-PF6),are chosen to fabricate various liquid crystal phases in aqueous solution respectively with three kind of nonionic amphiphilic molecules,viz.Brij-30(tetraethylene glycol lauryl ether),P123(EO20-PO70-EO20)and F127(EO100-PO70-EO100).The phase behaviors of those systems and the interactions between such molecules are fully discussed.In IL-containing systems,various interactions between EO-ILs(hydrogen bonding)and lipotropy-ILs(hydrophobic interaction)play key roles in LLC formation.Additionally,the cation[Bmim]+ with a hydrophobic butyl group tends to act as a cosurfactant and cooperate with the block copolymer in forming interfaces, thus enhancing the structural order.And also,as a melting salts,the ionic liquid(IL) may have a salting-out effect on the block copolymer system,which is helpful for formation of self-assembled structures.The good stability of such system is due to strong interactions mentioned above.According to the structural parameters of LLC derived from SAXS measurement,the stacking of surfactant molecules will be in a looser manner when doping ILs into Brij-30/water lamellar phase.The difference of amphiphilic nature between two used ILs makes Bmim-PF6 tend to stay at the interface of polar/apolar section,whereas Bmim-BF4 molecules like to locate in water regions as well as in polar domains.The additional thermal analyses by DSC and SAXS suggest a pseudo-hexagonal columnar structure appeared at low temperature in Brij-30/IL/H2O ternary systems,while the reverse micelle at high temperature.There are mainly lamellar and hexagonal phase formed in P123/IL/H2O systems,however hexagonal and cubic phase are dominant in F127/IL/H2O systems.Bi-lamellar structures are observed in P123/Bmim-PF6/H2O ternary system,which keep a continuous lamellar region with the change of content ratio of Bmim-PF6 and H2O.Furthermore, bicontinuous cubic and tetragonal phase are also obtained respectively in F127/Bmim-PF6/H2O and F127/Bmim-PF4/H2O.Our effort for fabricating organized molecular assemblies in ILs will be beneficial to the application of such self-assemblies as "green" template and micro-reactor,furthermore it is helpful to deeply discuss the weak non-covalent interactions for molecules.Special thanks are due to the National Natural Science Foundation of China for financial support(20373035,20573066,20773080).
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