| Gemini surfactants have recently attracted many attentions in surfactant field because of their novel self-assembly behavior brought by their unique molecule structure. The presence of special functional groups in a Gemini surfactant structure would produce additive weak molecular interactions, which may affect their self-assembly behavior and system properties. In this thesis, series of Gemini surfactant containing hydroxyl head groups named Alkanediyl-α,ω-bis[di(2-hydroxylethyl) dodecylammonium bromide], abbreviated as 12(2OH)-s-12(2OH), where s=3, 6, 8 and 10 respectively, have been investigated. The main results were shown below:1. The dilational rheology behavior of adsorption film formed by 12(2OH)-s-12(2OH) on the air/liquid phase was investigated using interfacial dilational rheology measurements. The effects of oscillating frequency, bulk concentration and spacer length on the dilational behavior of 12(2OH)-s-12(2OH) were illustrated. The spacer length of Gemini surfactants has a tremendous effect on the interfacial dilational rheology behavior of films formed by 12(2OH)-s-12(2OH). The variation of dilational modulus of 12(2OH)-8-12(2OH) with concentrations shows two peaks. This phenomenon is attributed to different configurations adopted by the spacer, revealing the effects of dynamic configuration of spacer on surfactant interfacial adsorption. The Lucassen/vanden Tempel(LVT) fitting results showed that the presence of hydroxyl head groups on Gemini surfactants can promote the interfacial elasticity of the adsorption films.2. The rheological properties of functional Gemini surfactant 12(2OH)-3-12(2OH) in the presence of small amount of traditional carboxylate surfactant, Sodium Laurate(SL), Sodium Myristate(SM) and Sodium Palmitate(SP), respectively, were investigated by steady state and dynamic rheological measurements. It was found that the addition of small amount of anionic surfactants has an obvious effect on the viscoelasticity of 12(2OH)-3-12(2OH) solutions. The molar ratio(β) of anionic surfactant in mixed solution was 0.3, the zero shear viscosity reached a maximum of 12.35 Pa×s and the G?∞ reached 31.88 Pa. When β=0.4, G?∞ was 14.67 Pa. The viscoelasticity of solutions decreased with shortened length of hydrophobic chain in anionic surfactant. When the concentration of 12(2OH)-3-12(2OH) increased to 60 mmol×L-1, the zero shear viscosity and G?∞ were also increased to 33.92 Pa×s and 46.41 Pa, respectively.3. The adsorption behavior of 12(2OH)-3-12(2OH) on the Si O2 nanoparticles and the foam stability of the modified nanoparticles were investigated. The comparison was made with that of traditional quaternary ammonium surfactant DTAB and Gemini surfactant 12-3-12. The distance between two ionic head groups of Gemini surfactants were shortened due to shorter spacer. The charge density of head group was thus increased, which leads to stronger electrostatic attractions between negatively charged Si O2 nanoparticles and surfactants. Consequently, the adsorption efficiency of Gemini surfactant at Si O2 nanoparticles surfaces was much higher than that of traditional surfactants. A longer foam stability time was achieved by 12-3-12/Si O2 system, which is 50 times of that of DTAB/Si O2 system. The adsorption amount and the adsorption efficiency of Gemini surfactant 12(2OH)-3-12(2OH) was lower than those of Gemini surfactant 12-3-12 because of larger hydroxyl containing head groups. Compared with 12-3-12/Si O2 system, the foam stability of 12(2OH)-3-12(2OH)/Si O2 system was enhanced by hydrogen bonds formed between Gemini surfactant molecules due to the presence of hydroxyl groups. The elasticity of the interfacial films were strengthened as well. |
