The Formation Of The Microemulsion In The Mixed Surfactant Systems

The phase behavior for the systems of Cetyltrimethylammonium bromide (CTAB)/poly- ethyleneglycol (9) monododecyl ether (AEO9) and CTAB/Octylphenol polyoxyethylene-10- ether (Triton X-100) have been studied in this thesis. The middle-phase behavior and solubili -zation for the microemulsions systems of CTAB/AEO9/alcohols/oils/brine and CTAB/ TX-100/ alcohols/oils/brine have been studied withε-βfishlike phase diagram method, and the effects of different alcohols, oils, temperature and inorganic salt (NaCl) on the middle-phase behavior of microemulsion formed by composile CTAB/AEO9 (TX-100) microemulsions systems were also investigated systematically. The phase diagrams of the pseudo-ternary-component of CTAB/ AEO9 (TX-100)/n-butanol/n-octane/water or brine systems were studied by dilution method, and then the microstrctures of microemulsions were determined through conductance technique, and the method of preparing Al2(WO4)3 precursor in the W/O microemulsion region was studied. Which provide valuable theoretical basis for preparing nanoparticles through microemulsion technology. This thesis contains four chapters:Chapter I. IntroductionSignificance and various types of mixed surfactants systems were introduced. The structure and characteristic of microemulsion were also overviewed. And the formation mechanism of microemulsion was introduced in detail: Instantaneous negative interfacial tension theory, Double film theory, Geometry theory, R ratio theory. The application and research methods of microemulsion were investigated. At last, the legislative basis and the contents of this thesis were summarized.Chapter II. Studies on the middle phase behavior of the microemulsion formed by CTAB/AEO9 mixed surfactants systemsThe middle-phase behavior and solubilization for the microemulsion system of cetyltrimethy -lammonium bromide (CTAB) and poly-ethyleneglycol (9) monododecyl ether (AEO9) have been studied withε-βfishlike phase diagram method. The effects of different alcohols, oils, temperature and inorganic salt (NaCl) on the middle-phase behavior of microemulsion formed by composile CTAB/AEO9 systems were also investigated systematically.1. Fromε-βfishlike phase diagrams, the microemulsion phase inversion Winsor I→III→II was observed with the increase in the alcohol concentration. Whether a small amount of AEO9 added into the CTAB system, or a small amount of CTAB added into the AEO9 system, the solubilization of the microemulsion formed by mixed cationic and nonionic surfactants is more effective than the single surfactant system.2. With the increase in the mass fraction of NaCl in aqueous phase, the amount of alcohol (εE) used to form single phase microemulsion decreases, and the solubilization power of the microemulsion system increases. The order of the solubilization power is 10 % > 7.5 % > 5 % > 2.5 %.3. The longer the carbon chain length of alkane is, the more alcohol needed to form middle phase microemulsion is. The solubilization power order is n-hexane > n-heptane > n-octane.4. The temperature has some effect on solubilization power of the microemulsion systems formed by CTAB/AEO9 microemulsion systems. The order of the solubilization power is 40℃> 50℃> 25℃> 30℃.5. The ability to form middle phase microemulsion and the solubilization power increase with its carbon chain length increases.Chapter III. Studies on the middle phase behavior of the microemulsion formed by CTAB/TX-100 mixed surfactants systemsThe middle-phase behavior and solubilization for the system of cetyltrimethylammonium bromide (CTAB) and Octylphenol polyoxyethylene-10-ether (Triton X-100) have been studied withε-βfishlike phase diagram method. The effects of different alcohols (n-butanol, n-propanol), oils (n-hexane, n-heptane, n-octane) and inorganic salt (NaCl: 5 %, 7.5 %, 10 %) on the middle-phase behavior of microemulsion formed by composile CTAB/TX-100 systems were also investigated systematically. Finally, we compared the effects of different factors on the phase behavior of microemulsions formed by CTAB/AEO9 and CTAB/TX-100 systems.1. The solubilization of the microemulsion formed by mixed cationic and nonionic surfactants is more effective than the single surfactant system.2. Adding inorganic salt (NaCl) facilitates the microemulsion inversion.3. The oils with shorter carbon chain lengths and the alcohols with longer carbon chain lengths are of higher solubilization power of their microemulsions systems.4. Comparing the effects of different factors on the phase behavior of microemulsions formed by CTAB/AEO9 and CTAB/TX-100 systems, we can see that the solubilization of CTAB/AEO9 microemulsion is higher than that of CTAB/TX-100 system under the same conditions, while the impact on the two systems with the factors are almost the same. Chapte IV. Studies on the structure of microemulsion formed by the mixed surfactants systems by conductivityThe phase diagrams of the pseudo-ternary-component of CTAB/AEO9/n-butanol/n-octane/ water and CTAB/TX-100/n-butanol/n-octane/water systems were studied by dilution method. The microstrctures of microemulsions were determined through conductance technique, and the method of preparing Al2(WO4)3 precursor in the W/O microemulsion region was studied.1. The single-phase microemulsion region of CTAB/AEO9/n-butanol/n-octane/water system is larger than that of CTAB/TX-100/n-butanol/n-octane/water system, the addition of inorganic salts reduced the single-phase microemulsion of the two systems.2. Three types of microemulsion microstructure can be identified from the conductivity curves of CTAB/AEO9 (TX-100)/butanol/octane/water microemulsion systems: W/O, O/W and BC. Conductivity increases linearly with the increase of water content at the beginning, and then increased slowly to reach the maximum, the conductivity begin to decline with the further increasing of the water content.3. From the conductivity curves of CTAB/AEO9 (TX-100)/butanol/octane/brine microemulsion systems, we can see that conductivity of the brine system changes almost the same as that of the water systems with a small amount of water. And then conductivity showed a nonlinear increase with the increase of brine. Finally, conductivity increases linearly. Therefore, the whole single- phase microemulsion area is divided into W/O, BC and O/W based on the two turning point in the electrical conductivity curve of brine microemulsion systems .