Dilational Viscoelasticity of the Zwitterionic Gemini Surfactants with Polyoxyethylene Spacers at the Interfaces

Abstract

The dilational viscoelasticity of zwitterionic gemini surfactants C₈E_xNC₁₂ with polyoxyethylene spacers at the water-air and water-decane interfaces were investigated by oscillating barriers method. The experiments were carried out at different concentrations with an accessible frequency range of 0.005 to 0.1 Hz. Interfacial tension relaxation method was employed to obtain dilational parameters in a reasonably broad frequency range. Experimental results show that the values of dilational elasticity and viscosity of C₈E_xNC₁₂ are larger than those of common nonionic surfactants, such as T × 100, and the dilational viscoelasticity at the water-decane is close to that at the water-air interface on the whole_. The results may be attributed to Coulombic attraction, and the possible schematic diagrams of adsorbed molecules with different polyoxyethylene spacers at the water-air and water-decane interfaces are proposed. We also analyzed C₈E_xNC₁₂ from the results of relaxation experiments and Cole-Cole plots.

Keywords:

• Cole-Cole plots
• dilational viscoelasticity
• interface
• polyoxyethylene spacer
• zwitterionic gemini surfactant

Acknowledgements

The authors are thankful for the financial support from the National Science & Technology Major Project (2011ZX05011-004), National High Technology Research and Development Program (2008AA092801), and the Knowledge Innovation Program of the Chinese Academy of Sciences (KJCX1-YW-21-03) of China.