Structure and Rheology of Wormlike Micelles Formed by Fluorocarbon-Hydrocarbon-Type Hybrid Gemini Surfactant in Aqueous Solution

The structure and rheological properties of wormlike micelles formed by a fluorocarbon hydrocarbontype hybrid gemini surfactant in an aqueous solution were investigated by means of small-angle X-ray scattering (SAXS) and viscoelastic measurements. The cross-sectional structure (the radius of the hydrophobic core and the thickness of the hydrophilic shell) and the aggregation number per unit axial length of wormlike micelles were evaluated by a model fitting analysis of SAXS profiles. Both parameters for the hybrid gemini surfactant were smaller than those of a corresponding hydrocarbon-hydrocarbon-type gemini surfactant. On the other hand, the viscosity of the hybrid gemini surfactant was higher than that of the hydrocarbon hydrocarbon-type gemini surfactant. From the viscoelastic parameters, the steady state compliance, J(e), and the terminal relaxation time, tau(w), which were independently obtained by dynamic viscoelastic measurement, we revealed that a larger number of entanglements and a longer contour length of the hybrid gemini surfactant led to the higher viscosity. These results obtained by the rheological measurements were consistent with those obtained by SAXS analysis.