| Among the exploration and practice of green chemistry, ionic liquids (IL), as a new kind of green solvents, occupy such unique properties that other liquids cannot compare:non-volatile, good thermal stability, high conductivity, etc. So they have recieved great attention in industry and academics fields among the past few decades. Surfactants are closely related to our everyday life and production, and they can self-assemble into various types of aggregates in solutions, such as micelles, liquid crystals, vesicles, microemulsions, etc. And because of these aggregates, surfactants have played an important role in materials, food, energy, pharmaceutical and many other fields. Recently, series of surface active ILs have been synthesized, which possesses the features of both surfactants and ILs and can also self-assemble into various molecular aggregates in solutions. Colloidal particles, often referred to as "artificial" atoms, can self-assemble to form colloidal particle clusters, one-dimensional nanowires, two-dimensional arrays and three-dimensional super crystals, etc. Using asymmetric type colloidal particles as building units can enhance the anisotropy of construction units. Then through the complex, directional and controllable self-assembly of the constructing units can realize the diversification of building structure and make their functions even more powerful, thus greatly expand the application fields of colloidal particles and enhance their inherent values.This dissertation is focused on two types of self-assembly. In molecular self-assembly we made a combination of surfactants and ILs:A pyrrolidine type surface active IL was synthesized, and their self-assembled aggregates in aqueous solutions were studied; While in colloidal particle self-assembly, at first silica nanowires were synthesized through a wet-chemical process, and the corresponding Pickering emulsions stabilized by them were discussed; Then the asymmetric modification of colloidal particles through the glancing angle deposition (GLAD) process was briefly discussed. There are three main experimental studies in this dissertation:1. Investigation of the self-assemblies formed by C16MPBr in aqueous solution:(1) By use of a molecule (AzoNa) which contains an azobenzene group as a photo-responsive switch, a wormlike micelle system which could reversibly response to UV and visible light was constructed. Under UV light irradiation, the molecular structure of AzoNa could undergo a transition from trans to cis state. As calculated from the 1H NMR spectrum of aromatic protons in this azobenzene derivative molecule, after exposed to UV-light for 30 min, the fraction of cis-AzoNa increased from 34% to 95%. The absorbance spectra of the AzoNa further confirmed the trans-cis transition of AzoNa. It also can be found that within 30 min, a photostationary state was attained. The photo-induced trans-cis transition of AzoNa was also reversible, which means that if the UV-irradiated solution was subsequently irradiated by visible light for about 24 hours, the cis-isomer could transition back to trans-AzoNa. This result proves the reversible trans-cis photoisomerization of AzoNa. When a certain amount of AzoNa (40-80 mM) was added to a 100 mM C16MPBr aqueous solution, a highly viscoelastic gel-like solution was formed. However, after UV irradiation for 30 min, the sample changed into a runny fluid with much lower viscosity. Results of rheology and cry-TEM proved that this drastic decrease in viscosity may be attributed to the transition from wormlike micelles into spherical micelles. The UV light induced isomerization of AzoNa directly leaded to significant changes in their molecular structures, which altered the geometry of the two molecules and their hydrophobicities, thus further influence the packing and association of C16MPBr and AzoNa. As a result, the initial formed wormlike micelles were greatly shortened in length and could not entangle with each other, resulting in a transition from wormlike to spherical micelles, and a sharp drop of the viscosity value in macroscopic scales.(2) A novel hydrogel was constructed by C16MPBr and sodium salicylate (NaSal). With the addition of NaSal, the viscosities of the 100 mM C16MPBr solutions firstly increased significantly, reaching the maximum of about 570 Pa·s where the concentration of NaSal was 60 mM. And the increase of viscosity was due to the initial formed spherical micelles grow in length and form the long, flexible wormlike micelles. These micelles may intertwine with each other and entrap the water molecules. Finally, the three-dimensional network structures are formed, which directly leads to the formation of the hydrogel. Then with the further addition of NaSal, the viscosities decrease, which was caused by the formation of branched micelles. Results of1H NMR, FT-IR, SEM, and rheological measurements proved that both the NaSal concentration and pH have significant effects on the formation and properties of the gels. The gel structure was strongest when the concentration of NaSal was 60 mM and pH was 9.70. Hydrophobic and electrostatic interactions are considered as the main driving forces to form the gels.2. Investigation of the new Pickering emulsions stabilized by silica nanowires. Both hydrophilic and amphiphilic silica nanowires were synthesized using a wet-chemical method. The hydrophilic silica nanowires are about 1,5 and 10 μm in length, respectively, and range in diameter from 200 to 250 nm. While the amphiphilic silica nanowires have a diameter ranges from 200 to 250 nm, and a length of about 1.5,2.5 and 5 μm, respectively. Oil-in-water emulsions were formed with hydrophilic silica nanowires, and the emulsions stabilized by the 10 μm hydrophilic silica nanowires were stable after 4 months, while emulsions stabilized by the 1 μm and 5 μm hydrophilic silica nanowires were completely demulsified after 3 and 7 days separately. SEM images showed that the 1 and 5 μm hydrophilic silica nanowires were distributed on the paraffin surface dispersedly and only little amount of the nanowires can be observed at the surface of the droplet. Most of the silica nanowires moved into the water phase from the emulsion droplet surface. While the 10 μm hydrophilic silica nanowires tended to intertwine with each other and form a two-dimensional network onto the paraffin surface, which is beneficial for the emulsion droplet stabilization. Water-in-oil emulsions can be successfully formulated by the amphiphilic silica nanowires of three different length, and the emulsions kept stable even after 4 months. SEM images showed that amphiphilic silica nanowires distributed homogeneously on the droplet surface and closely packed between each other, forming a quite stable monolayer, which greatly contributed to the stabilization of the emulsion droplets. The effect of amphiphilic silica nanowire length, concentration and the oil to water volume ratio on the water-in-oil emulsions were discussed:increasing the length and concentration of the nanowire were benefit for the stabilization of the emulsions; when the oil volume fraction was increased to 0.2, a catastrophic phase inversion from oil-in-water to water-in-oil occurred.3. Asymmetric modification of colloidal particles through GLAD process was investigated. Firstly, micrometre sized PS particles with uniform size distribution were synthesised through a dispersion polymerization reaction. Then the PS particles were self-assembled at water/air interface to form a two-dimensional monolayer colloidal crystals. After the transition process of the monolayer into hydrophilic glass substrates, GLAD was conducted to modify the PS particles with Au patches. The incident angle of Au steam was controlled at 10 °in the GLAD process. The monolayer was inverted for 180 ° before the second GLAD modification, which resulted in two separated Au patches distributed on two sides of the one half particles. The PS particle array in the monolayer was inhomogeneous, which made the geometry morphology of the Au patches quite different. There were patches with rectangles, triangles and isosceles triangles morphology after the GLAD modification. Then chemical etching of the patches was conducted in order to further decrease the patch area. And the area of patches with isosceles triangle morphology were greatly decreased after 3.5 min etching, almost like Au dots distributed on the particles. Finally, the monolayer was printed and overturned using PDMS, after which the PS particle array was deposited on PDMS. GLAD can be conducted several times to modify PS particles with more Au patches distributed at three dimensions. |
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