| This thesis mainly studies the phase behavior and solubilization of the microemulsion systems formed by the zwitterionic surfactant dodecyl sulfobetain (DSB). It contains three chapters. Chapter I. Introduction. Chapter II. Studies on the middle phase behavior of the microemulsion formed by dodecyl sulfobetain (DSB). Chapter III. Studies on the phase behavior of the microemulsion formed by DSB with Winsor phase diagram and the calculation of related parameters. Chapte IV, The phase behavior of the microemulsion formed by DSB with different ratios of oil to the plus of water and oil.Chapter I. IntroductionDodecyl sulfobetain (DSB) is a kind of zwitterionic surfactant, which has low toxicity and irritation to skin, has no social effects of pollution, and is biodegradable easily and is able to bear the hard water and the high concentration of electrolyte. DSB is widely used in the feed additives, the pharmaceutical industry, agricultural and forest production, food additives, daily chemicals and other fields. In recent years, the research about the zwitterionic surfactant has received wide attention.The definition, classification and property such as isoelectric point were introduced in this chapter. The progress and the application in the research of the zwitterionic surfactants were summarized.Chapter II. Studies on the middle phase behavior of the microemulsion formed by dodecyl sulfobetain (DSB)The phase behavior of the quaternary microemulsion systems dodecyl sulfobetain (DSB)/alcohol/alkane/water was studied withδ-γandε-βfishlike phase diagrams, respectively. The effects of different oils, alcohols, aqueous compositions (NaCl contents and pH values) on the phase behavior and the related parameters were investigated. 1. Fromδ-γandε-βfishlike phase diagrams, the microemulsion phase inversion Winsor I (2)→III (3)→II ( 2 ) was observed with the increase in the alcohol concentration.2. The fish head in theδ-γfishlike phase diagram is upward, which indicates that part alcohol dissolves in the interfacial layer and the other part dissolves in oil. The composition of the HLB plane was calculated by using the HLB equation.The average solubilities of surfactant and alcohol in the water and oil phases were obtained by thr mass balanced equation.The longer the alcohol carbon chain or the shorter the oil carbon chain length is, the smaller the values of AO,W and AS are, and the larger the solubilization power of the system is. The NaCl concentration and pH value have a little influence on the formation of the microemulsion.3. In contrast to theδ-γfishlike phase diagram, the fish head in theε-βfishlike phase diagram is downward.The phase behavior of the microemulsion was researched and the related physicochemical parameters were calculated more accurately by theε-βfishlike phase diagram.Chapter III. Studies on the phase behavior of the microemulsion formed by DSB with Winsor phase diagram and the calculation of related parameters The phase behavior of the quaternary microemulsion system dodecyl sulfobetain (DSB)/1-butanol/alkane/brine (5%NaCl) was studied with Winsor phase diagram in this chapter.1. The HLB equation of the Winsor phase diagram was deduced.2. The larger the DSB concentration is, the larger the minimum alcohol content needed to form middle phase microemulsion is. However, the alcohol width increases first and then decreases along with the increase in the DSB concentration.3. The minimum alcohol content needed to form middle phase microemulsion and the alcohol width increase, as the oil carbon chain length increases.It is because the oils with shorter carbon chain lengths can easily penetrate the palisade layer of the microemulsion droplet, making the mean curvature of the interfacial layer turn toward oil.Chapter IV. The phase behavior of the microemulsion formed by DSB with different ratios of oil to the plus of water and oilThe solubilities of surfactant and alcohol in the oil and water phases, SO,SW and AO,AW, were calculated using theε-βfishlike phase diagram with different ratios of oil to the plus of water and oil (α).The effects of different alcohols, oils and aqueous compositions (NaCl contents and pH values) on the phase behavior were investigated at 40°C andα=0.667.1. The longer the carbon chain length of the alcohol, the easier to form the microemulsion, which was attributed to the higher ability to change the hydrophilicity of the alcohol molecules with longer carbon chain length.2. The amount of alcohol needed to form the middle phase microemulsion is increased as the carbon chain length of the oil increases. The explaination is that the smaller alkane molecule is easier to penetrate into the barrier of the interface, which makes the amphiphilic layer hydrophobic.3. Salt concentrations and pH values have little influence on the formation of the microemulsion.
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