Studies On The Surface Adsorption And Microemulsion Phase Behavior Of Surfactant-like Lonic Liquids

This thesis contains four parts. Chapter I, Introduction;Chapter II, Studies on the aggregation behavior of the surfactant-like ionic liquid C12mimBr at the air-liquid interface by the dilational rheology method;Chapter III, Studies on the interfacial composition, thermodynamic properties and structural parameters of the W/O microemulsions containing CnmimBr; Chapter IV, Synergic effect of SDS and C16mimBr on the interfacial composition and thermodynamics of the W/O microemulsions.Chapter I. IntroductionSurfactant-like ionic liquids, such as 1-dodecyl-3-methylimidazolium bromide (C12mimBr),1-tetradecyl-3-methylimidazolium bromide (C14mimBr) and 1-hexadecyl -3-methylimidazolium bromide(C16mimBr)were introduced. The dilational rheology method used in the research of the aggregation behavior of a surfactant at the air-liquid interface, and the W/O dilution method used in studying the phase behavior of microemulsions were summarized. The progress in the research of the dilational rheology method and the W/O dilution method were reviewed.Chapter II. Studies on the Aggregation Behavior of the 1-dodecyl-3- methylimidazolium bromide at the Air-Liquid Interface by the Dilational Rheology MethodThe aggregation behavior of the surfactant-like ionic liquid C12mimBr at the air-liquid interface was studied by the dilational rheology method. The effects of the C12mimBr concentration of the aqueous solution, salinity, temperature and the dilational frequency on the dilational viscoelasticity properties were investigated.1. The C12mimBr concentration has a notable influence on the dilational viscoelasticity properties. The results show that the dilational modulus gets a maximum value at first and then decreases with the C12mimBr concentrations. 2. Salinity and temperature could influence the dilational viscoelasticity properties of the C12mimBr solution. The higher the salinity or the lower the temperature, the larger the dilational modulus is. Both higher salinity and lower temperature favor the formation of the stable film of the C12mimBr molecules at the interface.3. Dilational frequency also influences the dilational viscoelasticity properties of the interface of the C12mimBr solution. Dilational modulus and dialtional elasticity increase significantly, and the dilational viscosity and the phase angle decrease with dilational frequency.Chapter III. Studies on the Interfacial Composition, Thermodynamic Properties and Structural Parameters of the W/O Microemulsions Formed by CnmimBr using the W/O Dilution MethodThe interfacial composition, thermodynamic properties and structure parameters of the W/O microemulsions formed by CnmimBr have been investigated with the W/O microemulsion dilution method. The effects ofωo (the molar ratio of water to surfactant), alcohols, alkanes, salinity and temperature on the above items were discussed.1. The size of the microemulsion droplet increases significantly with the water content. This property may be useful in preparing nanoparticles with different sizes using the W/O microemulsions with different water content as a template.2. The increase in the chain length of the surfactant or alcohol, or decrease in the alkane chain length can enlarge the size of the droplets. Increase in salinities also can enlarge the size of the droplets.3. Temperature affects the molecular geometry of the surfactant in the interface, which is unfavorable to the formation of the stable W/O microemulsion.Chapter IV. Studies on the Interfacial Composition and Thermodynamic Properties of the W/O Microemulsions Formed by SDS and C16mimBr mixtureThe interfacial composition and thermodynamics of W/O microemulsions formed by the mixture of the anionic sodium dodecyl sulfate (SDS)and the cationic C16mimBr were investigated by the dilution method. The effects of different alcohols, oils and salinity on the formation of the W/O microemulsions were also investigated.1. The W/O microemulsions for the C16mimBr/SDS/n-decane/1-butanol/water systems can be prepared within the range of the molar ratio of SDS to C16mimBr between 0-0.2 and 0.8-1.0.2. The synergic effect exists between SDS and C16mimBr on the accommodating hydrophile-lipophile property of the interface in the formation of W/O microemulsions. This may be attributed to the strong electrostatic attraction between cationic and anionic surfactants.3. Alcohols, alkanes and salinities all influence the molar fraction of alcohol at the interface, the solubility of the alcohol in the oil phase and the spontaneity of transferring alcohol from the continuous oil phase to the interface in the formation of the W/O microemulsions C16mimBr/SDS/alkane /alcohol/brine.4. Long chain alcohols were easier to penetrate into the interfacial layer and less amount of alcohols were needed to balance the hydrophile-lipophile property of the interface. The short chain alkanes have higher efficiency to form W/O microemulsions.Higher salinities promote the formation of W/O microemulsions and therefore decrease the content of the alcohol needed to form W/O microemulsions.