Aggregation Of The Quaternary Ammonium Gemini Surfactants In Apolar Solvent Studied By Conductivity And Spectroscopy

Gemini surfactants are made up of two amphiphilic moieties connected at the level (or in the vicinity) of the head groups by a spacer group. The distance between the two head groups within a gemini molecule can be effectively controlled by the length of spacer chain, which strongly affects the charge density of the ionic head groups, the alkyl chain density of the surfactants molecule as well as the molecular geometry. As a result, the aggregation behaviors of the gemini surfactants in solution are complicated. However, few studies have related to the aggregation of gemini surfactants in apolar solvents. In this dissertation, we studied the aggregation of the quaternary ammonium gemini surfactants in apolar solvents by conductivity and spectroscopy. The primary work and the results are concluded as follows:The aggregation behavior of the reverse micelles formed by C₁₂-s-C₁₂·2Br (s=2,3,4,5,6,8) in n-heptane with the assistance of n-hexanol has been investigated by conductivity. The mechanism of electric conductivity was generally considered as the migration of the counter-ions (here is Br·) dissociated out in the cores through the membranes between the reverse micelles during the collision. The relative size of reverse micelles can be obtained by comparing W0,max, the mole ratio of water to surfactants at the maximum conductivity of reverse micelles. We investigated the influence factors of reverse micellar size from three aspects. Firstly, the effect of n-hexanol was examined at the same surfactants and found that the size of reverse micelles decreased with the increase of n-hexanol content in the system, which was attributed to the increase of n-hexanol content in the interfacial layer of the reverse micelles. The second aspect was related to the effect of spacer length. When fixed the n-hexanol content in the reverse micelles, the size of reverse micelles formed by C₁₂-s-C₁₂·2Br was different. The n-hexanol content in interfacial layer of reverse micelles was minimum when the water content reached W0,max, so the size of reverse micelles formed by C₁₂-4-C₁₂·2Br was the biggest. Finally, we examined the effect of temperature. When fixed both surfactants and the n-hexanol contents, the size of...