Molecular Interaction And Synergism In Cationic And Anionic Surfactant Mixtures Containing Gemini Component(s)

Self-assembly of cationic/anionic surfactant mixtures in aqueous solution depends on several factors. The hydrophobicity of the alkyl tails is the original driving force of aggregation. The interactions between the molecules strongly affect the organization behavior of the surfactants. The surfactant structure governs the geometry and the conformation of the molecule and thus determines the morphologies of the aggregates. When introducing gemini surfactant into the cationic/anionic mixtures, the hydrophobic effect is greatly enhanced due to the two tails of a gemini surfactant synergistically acting in one molecule. The distance between the two head groups of a gemini surfactant is constrainedly shortened by the spacer, which results in the considerable increase of the charge density on the head groups and hence the synergism between the oppositely charged components are considerably strengthened. The intermolecular weak forces are diversified owing to the introduction of the spacer into the gemini molecule. Furthermore, the two amphiphilic moieties connected by the spacer group at the level of, or in close vicinity to, the head groups, enables gemini surfactants adopt various conformations, which enriches the aggregate morphologies of the surfactants.In this dissertation, we focus on the cationic/anionic mixtures of C₁₂-3-C₁₂·2Br/SDS, C₁₂-2-EO_n-C₁₂·2Br(n= 1,2,3)/SDS, C(m-1)pPHCNa/C_mTABr(m= 10,12), C₁₂-2-EO₂-C₁₂·2Br/C9pPHCNa and 2C₁₂-s-2C₁₂·2Br(s=3,6,8)/C11pPHCH in aqueous solutions, in which C₁₂-3-C₁₂·2Br, C₁₂-2-EO_n-C₁₂·2Br(n=1,2,3) and 2C₁₂-s-2C₁₂·2Br(s=3,6,8) are cationic gemini surfactants, C(m-1)pPHCNa(m=10,12) are anionic gemini surfactants, and C_m TABr(m=10,l2), SDS are conventional surfactants, respectively.Since the two series of compounds 2C₁₂-s-2C₁₂·2Br(s=3,6,8) and C(m-1)pPHCNa(m=10,12) were synthesized for the first time in our laboratory and their properties were not reported before us, we previously examined the properties of the individual gemini surfactants [97,98,102]. Besides, we also examined some properties of individual C₁₂-s-C₁₂·2Br and C₁₂-2-EO_n-C₁₂·2Br [99～101]. These results have been excluded from this dissertation except for the necessary data listed in Supplementary information (II) for the discussion on the examined binary mixtures.The self-assembly of the surfactant mixtures at the air/water interface and in the bulk solutions were examined by the following techniques. The adsorption and spreading of the mixtures at the air/water interface were examined by equilibrium or dynamic surface tension measurements and Langmuir monolayer technique. The mixed miceilization of the systems were dealt by the steady and time-resolved fluorescence spectra analysis. The rheological behaviors of the mixed surfactants...