Viscosity of Cationic Gemini Surfactant/NaSal Solutions

Gemini surfactants possess two hydrophilic heads, two hydrophobic tails and one connecting group. This unique structure is different from the traditional surfactant structure, which usually composes of only one hydrophilic head and one hydrophobic tail. Therefore, Gemini surfactants have different properties from the traditional ones. It is a kind of surfactant most likely to receive extensive attention and to have more and more applications in twenty-first Century. When surfactant solution is subjected to different shear forces, the viscosity changes due to the corresponding changes in micelle structures among the spherical, rod and reticulate in the solution. In order to investigate the transition of micelle structures of Gemini surfactant solutions, and provide guidance for the application of turbulent drag reduction, the viscosities of solutions with the surfactant concentration ranging from 2.829 mmol/L to 7.072 mmol/L were determined at 25℃ under different shear rates. In this work, Physica MCR 302 Advanced Rotational Rheometer produced by Anton Paar company was employed. To achieve reliable measurement results, the coaxial double cylinder test system DG42 was chosen. In the relatively high concentration solutions, the viscosities decreased rapidly to a fixed value over time at high shear rates, which reflected simple micellar transitions here. However, the micellar transitions became complex in the relatively low concentration solutions. The viscosity decreased at first, followed by increasing and then decreasing again on the basis of an oscillation mode at high shear rates. Under low shear rates, there is a transient “stress response process” for all surfactant solutions at beginning, resulting in the increase in viscosity. However, the trends of viscosity change are similar for all samples upon increasing shear time. All of them increase firstly and then decrease, and finally tend to be stable, therefore the micellar transitions should be similar.