The Orderly Shift Aggregate Microstructure Induced By Ionic Liquid Surfactant Research

The synthesis and application of ionic liquid surfactants, not only extends the types and quantities of the ionic liquids and surfactants, but also enhance the communication and connection between the two types of materials, which will expand the new applications and play important role in scientific research, industrial production and daily life.Recently, imidazolium-type ionic liquid surfactants are easy to be synthesized and the raw materials are low prices, so the species of such ionic liquids have been attracted a great attention studies of the effect of ionic liquid surfactants on the micro structure change of molecular assemblies will provide a important thearetical basis for the adjusting of moleculer assemblies and the exploring of the assemblies.1. Ionic Liquid Surfactants Synthesis and Induction of AOT Vesicle FormationThe N-methyl imidazole and bromide alkyl hydrocarbons were used to synthesis bromo-l-alkyl-3-methylimidaz olium surfactant (CnmimBr, n=8,12) by one step nucleophilic substitution reaction.The ionic liquid surfactants l-alkyl-3-methy limidazolium bromide (Cn mimBr,n=4,8.12). The turbidity, dynamic light scattering (DLS), negative-stained transmission electron microscopy(TEM),ζ-Potential measurements, isothermal titration microcalorimetry were used to investigated the microstructural transformation of1,4-bis(2-ethylhexyl) sodium sulfosuccinate (AOT) aggregates from micelles to vesicles. The ionic liquids with a hydrophobic chain structure show hige surface activity. The can effectively induce micelles changed to be the single-wall vesicles. The surfactant concentration required for inducing the changes from micelles to vesicles is significantly reduced with the increase of the length of the hydrophobic chain. The size of the formed vesicles is uniform, the vesicles show high thermal stability and charge controllability. In addition, increasing the length of alkyl chain ionic liquids can effectively reduce the initial concentration of inducing AOT microstructural changes. Based on the template of AOT vesicles, the Polypyrrole hollow spheres were obtained, which will provide a novel path for the preparation of hollow spheres.2. The Influence of DODAC Vesicles Microstructure by Ionic Liquid SurfactantsThe interaction of ionic liquid1-dodecyl-3-methy limidazolium bromide (C12mimBr) with double-octadecyl-dimethyl ammonium chloride (DODAC) vesicles was systematically investigated by the phase diagram, turbidity, dynamic light scattering (DLS), freeeze-etched transmission electron microscopy, isothermal titration microcalorimetry (ITC), nano-differential scanning calorimetry(nano-DSC), ζ-potential measurements and nuclear magnetic resonance (NMR). The results show that, a hexagonal liquid crystal phase and monophase liquid district were formed in C12mimBr/DODAC/H2O system. The monophase liquid district was composed of microemulsion and vesicle phases. In the5.0mM DODAC vesicles system, the turbidity was increased gradually with the increase of C12mimBr. When the C12mimBr concentration is10.0mM, the turbidity reaches a maximum, then the turbidity decreases with the increasinge on C12mimBr concentration, indicating that the binding of on DODAC vesicles ocurred. Dynamic light scattering indicates that the vesicle hydrodynamic radius RH decreases initially with C12mimBr concentration increased to10.0mM, then the hydrodynamic radius of vesicles increased gradually with the increases of C12mimBr concentration. This indicates that the addition of ionic liquid did not destroy vesicles, however, make the structure of vesicles changes. The addition of low concentration C12mimBr make vesicles arranged more compacted, so its size decrease, but the vesicle size distribution is wide, then, it increases gradually with C12mimBr added, which can be confirmed by the TEM images of vesicles. ITC indicated that the bingding process of C12mimBr with DODAC vesicles is divided into two stages. Before the concentration of13.9mM of C12mimBr, the interaction enthalpy of the ionic liquid surfactant and vesicle change from exothermic (-600cal/mol) to endothermic heat (700cal/mol), which further verified that the addition of ionic liquid surfactant C12mimBr alters the moleculer chain arrangements of DODAC vesicles, then, C12mimBr bound to the vesicle surface. Differential scanning microcalorimetry showed that the DODAC vesicles exist two phase transition:pre-transition Tm1and chain melting transition Tm2. With the increasing concentration of C12mimBr, Tm1and Tm2were both reduced gradually, indicating that the addition of ionic liquid changed the chain microstructure of vesicles. Zeta potential and NMR showed that in the process of interaction between ionic liquids and vesicles, the C12mimBr molecular alkyl chain maybe probably located in non-polar microdomain of vesicles. Due to charge repulsion with DODAC molecules, the positively charged imidazole ring may be located in amphiphilic microdomain of DODAC vesicles to form a loose structure, which shield the vesicle surface charge. As a result, the addition of ionic liquid can adjust structure and properties of DODAC vesicles, which provides a new way for controlling the structure and properties of biomimetic membranes.3. The Influence of Porphyrin Molecules Aggregation Behavior by Ionic Liquid SurfactantsPorphyrin molecules have strong π-π stacking due to their special large ring structure. In aqueous solution, they can easily form aggregates which is driven by hydrogen bonding, hydrophobic interaction and electrostatic attraction. Ionic liquid surfactants have a good surface activity, and can form micelles in aqueous solution. In the presant work, the UV-vis spectroscopy, isothermal titration calorimetry, fluorescence spectroscopy, ζ potential measurements, pH measurement and other experimental methods were used to study the structure changes of porphyrin aggregates induced by ionic liquid surfactants in aqueous solution. In addition, porphyrin aggregate structural changes on the effect of hydrophobic chain length of ionic liquid was also discussed. It was found that the ionic liquid surfactants can induced the structural changes of porphyrin, and the longer the chain length of the alkyl chain, the stronger the ability of the ionic liquid surfactants to induce the aggregate transition.