Aggregation and thermodynamic properties of ionic liquid-type gemini imidazolium surfactants with different spacer length

• Published in: Colloid and polymer science 2009-04, Vol.287 (4), p.395-402
• Main Authors: Ao, Mingqi, Huang, Peipei, Xu, Guiying, Yang, Xiaodeng, Wang, Yajing
• Format: Article
• Language: English
• Subjects: Adsorption efficiency; Agglomeration; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Colloidal state and disperse state; Complex Fluids and Microfluidics; Exact sciences and technology; Fluorescence; Food Science; General and physical chemistry; Ionic liquid-type gemini imidazolium surfactant; Light scattering; Micelles. Thin films; Micropolarity; Nanotechnology and Microengineering; Original Contribution; Physical Chemistry; Polymer Sciences; Resistivity; Sodium halides; Soft and Granular Matter; Spacer length; Spacers; Surface physical chemistry; Surfactants; Thermodynamic properties; Thermodynamics of micellization
• ISSN: 0303-402X; 1435-1536
• DOI: 10.1007/s00396-008-1976-x

The aggregation behavior and thermodynamic properties of micellization for the ionic liquid-type gemini imidazolium surfactants with different spacer length ([C₁₂-s-C₁₂im]Br₂, s = 2, 4, 6) have been investigated by means of surface tension, electrical conductivity, dynamic light scattering and fluorescence measurements. The values of cmc, γ cmc, Γ max, A min, π cmc, pc₂₀ and cmc/pc₂₀ suggest that the shorter the spacer, the higher the surface activity of [C₁₂-s-C₁₂im]Br₂ is. The cmc and γ cmc values are decreased significantly in the presence of sodium halides, and the values decrease in the order NaCl < NaBr < NaI. The thermodynamic parameters of micellization ( [graphic removed] , [graphic removed] , [graphic removed] ) indicate that the micellization of [C₁₂-2-C₁₂im]Br₂ and [C₁₂-4-C₁₂im]Br₂ is entropy-driven, whereas aggregation of [C₁₂-6-C₁₂im]Br₂ is enthalpy-driven at lower temperature but entropy-driven at higher temperature. Finally, the fluorescence measurements show that the micropolarity of micelles increases but the aggregation numbers decrease with increasing the spacer length of [C₁₂-s-C₁₂im]Br₂.