Vesicle Formation Based On Ionic Liquids And Their Applications In The Synthesis Of Nanomaterials

With the rapid development of the economics, there are more and more environmental problems which human needs to solve. Urgent exploitation and utilization of the future energy make the research and development of green chemistry to be a trend. Ionic liquids (ILs) have extensive applications because of its unique properties. The research of ILs has greatly promoted the development of green chemistry. With the successful synthesis of long-chain ILs, a kind of ILs with surface activities has been available. Exploring the properties and studying the self-assemblies formed by this kind of surface-active ILs are important to the ILs' development. It's also crucial for expanding the applications of ILs.Among the investigations of surfactants, studying of the self-assemblies is always the main issue. The formation of different kinds of self-assemblies makes the surfactants play important rules in life, energy, information, material, etc. Vesicle, as a kind of self-assemblies formed by surfactants, has its unique structure and properties. Many surfactants or their mixtures with other surfactants can form vesicle spontaneously in aqueous solution. Currently, most researches of vesicle are focused on the catanionic surfactant system. Vesicle has widely applications, for example, it can be used to simulate the bio-films, used as drug carrier, used in cosmetics and food industry, etc. With the development of nanotechnology, vesicle can also be used as soft template for the preparation of nanomaterials. It can provide appropriate micro environments for some chemical or biochemical reactions.This thesis focuses on surface-active ILs, self-assembly vesicle and preparation of nanomaterials. We have studied the phase behaviors, the phase diagrams and the rheological properties of the catanionic systems formed by mixing long-chain imidazolium ILs or long-chain N-methylpyrrolidinium based ionic liquids with different kinds of anionic surfactants and confirmed the vesicle formation. Corresponding nanomaterials have been synthesized by using the vesicle phase as the reacting solution. There are two parts in this dissertation as follows:1. The phase behaviors of a catanionic surfactant aqueous solution composed of a long-chain imidazolium IL 1-dodecyl-3-methylimidazolium bromide (C12mimBr and an anionic surfactant sodium dodecyl sulfate (SDS) have been studied. We have got the phase diagram by observing the samples with and without crossed polarizers and measuring the conductivities. The results indicate that when the concentration of C12mimBr is fixed on 100 mM, the sequence of the phase regions with increasing SDS amounts from 0 to 100 mM can be summarized as follows:L1 (micellar solution), L1/Lα, Lα(turbid), Lα(flow birefringence), L1/thick precipitate. The vesicle formation in the birefringent Lαphase has been confirmed by TEM and FF-TEM pictures. Rheological measurements were used to characterize the macroscopic properties of the vesicle phase which behaves like a Bingham fluid. Both electrostatic and hydrophobic interactions contribute to the vesicle formation in the catanionic system. Compared to the DTAB/SDS aqueous solution, differences between the imidazolium and trimethylammonium headgroups geometric packing and charge density induce the different phase behavior in each system. Silica hollow spheres, with diameters 30-60 nm and a wall thickness of 8-10 nm, were prepared by using the vesicle as the templates. The hollow silica spheres were characterized by TEM, scanning electron microscopy (SEM) and nitrogen adsorption-desorption. The pore diameter of the silica hollow spheres is about 4.0 nm. The pore volume and the BET surface area of the hollow silica spheres are 1.158 cm3/g and 805.9 m2/g, respectively. This surface area is relatively large compared to the surface areas for similar materials reported previously.2. The phase behaviors of an aqueous catanionic surfactant system composed of a long-chain N-methylpyrrolidinium based ionic liquid N-dodecyl-N-methylpyrrolidinium bromide (C12MPB) and a divalent metal surfactant copper dodecyl sulfate (Cu(DS)2·4H2O) are studied. When the concentration of C12MPB is fixed on 100 mM, the sequence of the phase regions with increasing Cu(DS)2·4H2O amounts from 0 to 100 mM can be summarized as follows:L1, L1/Lα, La(turbid), Lα/precipitate,L1/ thick precipitate. The vesicle formation in the birefringent La phase has been confirmed by TEM. The macroscopic properties of the vesicle phase were characterized by rheological measurements which behaves like a Bingham fluid like other catanionic vesicle phase. We have compared the C12MPB/Cu(DS)2·4H2O to C12MPB/SDS system and found that the electrostatic shielding of these two systems are different due to the different counterions, which induced the different phase behaviors. Vesicle can be formed in both of the two systems, it suggests that the driving forces of the vesicle formation are still the electrostatic and hydrophobic interactions. Leaf-like CuO sheets, which are 1-1.5μm in length and 300-400 nm in width, were prepared in the vesicle phase. The CuO crystals were characterized by TEM and X-ray diffraction measurements (XRD). In this reacting system, Cu(DS)2·4H2O is not only the constructing molecule for the vesicle, but also the Cu2+ -source for the synthesis of semiconductor nanomaterials.