The Thermodynamics Of Formation Of Surfactant Molecular Aggregates

The interactions of surfactants on interface of different solvent led to the formation of molecule aggregates (micelles, vesicles, microemulsion, lyotropic liquid crystals etc). Although it has been widely applied to industry and agriculture, the establishment and mechanism of surfactant molecule aggregates has been a research hotspot in the sufactant field. Due to the similarity of protein structure with micellar one, it is very useful idea to use the research methods of protein structure to study the structure of micelle and it allows the research on the structure of micelles. On the other hand, it is of practical significance to explore microemulsion with nonaqueous polar solvent as non-continuous phase, because there are always water-sensitive materials in the process of production. Therefore, this paper fall into the following aspects:1. The formation of SDS was investigated using the properties of urea. The critical micelle concentrations of SDS in aqueous solution at different temperature and urea concentration were obtained by conductance and the thermodynamic parameters dependence of temperature and urea concentration for the formation of SDS micelle were also obtained by the thermodynamics of micellar formation.2. AOT micelle formation in ethylammonium nitrate(an ionic liquid) was investigated by surface tension measurement in this paper and the critical micelle concentrations (CMC) of AOT in ethylammonium nitrate at different temperatures were obtained. The thermodynamic parameters of micelle formation were obtained according to the two-phase thermodynamic model. The results suggested that the micelle formation of AOT in ethylammonium nitrate was a spontaneous, endothermal and entropy-increasing process.3. The phase behaviors of AOT / dimethyl formamide (DMF) /cyclohexane at 25℃and AOT / dimethylsulfoxide/ cyclonexane microemulsion at 35℃was studied. The results show that single phase section could be formed at proper composition of the nonaqueous microemulsion system. UV-Vis study proved that the polar domain of dimethyl formamide or dimethyl sulfoxide exist in nonaqueous microemulsion system. In addition, Percolating phenomenon was further verified to exist by the study of conductivity of dimethyl formamide or dimethylsulfoxide/ cyclonexane nonaqueous microemulsion system and this provides theoretical basis for the study of the phase behavior and microstructure of the nonaqueous microemulsion.4. Investigation on the phase behavior of solution is significant theoretically and practically. In this paper, the phase behavior of TX-100/cyclohexane/EAN ternary system was investigated at 25℃, in which ionic liquid ethylammonium nitrate(EAN) is substituted for water as a green solvent. The results showed that the ternary system can form the single phase microemulsion at suitable condition. The electric conductivity was employed to determine that there exists two transition microemulsion region including IL/O and O/IL without bicontinuous region in the microemulsion in comparison to general microemulsion. Finally, the formation of the microemulsion with EAN as its polar domain was confirmed further by UV spectrophotometry.