Rheological properties of salt-free symmetry-quaternary ammonium gemini surfactants aqueous solutions

Abstract

The rheological behaviour of solutions of dimethylene-1,2-bis (tetradecyl ammonium bromide) (GS14-2-14), dimethylene-1,2-bis (hexadecyl ammonium bromide) (GS16-2-16) and dimethylene-1,2-bis (octadecyl ammonium bromide) (GS18-2-18) at a surfactant mass concentration of 20 g L⁻¹, is investigated, respectively, as a function of temperature and shear rate by dynamic-state rheological measurements. It is confirmed that the elastic or storage modulus (G′) and the viscous or loss modulus (G′′) are reduced first and then be equal under the increase of temperature. When the angular frequency is improved, G′ and G′′ appear to be increased first and then become straight. These results are in agreement with the prediction of linear viscoelasticity theory of pseudoplastic fluid. However, the quantitative analysis of the results (Cole–Cole plots, loss factor tgδ and dynamic viscosity η′(ω)) on the basis of the theory reveals some inconsistencies. Those results can be analysed by shear-thinning effect and shear-induced effect separately.

Keywords:

• cationic gemini surfactant
• salt-free
• dynamic-state rheological property
• shear-induced effect
• shear-thinning

Acknowledgements

This work was supported by the Natural Science Foundation of Shaanxi (2012JQ2004, 2012JQ2005) and the Shaanxi Major Scientific & Technological Innovation Projects (2011ZKC04-3).