Structural changes in a cationic surfactant-water mixtures

Abstract

Structure and structural changes in 3-tetradecyloxy-2-hydroxypropyl trimethyl ammonium bromide (R₁₄HTAB)/H₂O mixtures have been studied by steady and dynamic shear rheology. The results showed that the self-aggregate undergo two transitions in shape from spherical to rod-like micelles to viscoelastic wormlike micelles and to the hexagonal lytropic liquid crystal in the investigated concentration range. The transition of spherical micelles into rod-like micelles takes place above 300 mmol kg⁻¹. The overlap threshold micelle concentration is about 500 mmol kg⁻¹, and the η₀ and R₁₄HTAB concentrations give relationship of the power law, i.e. . The microstructure of the formed micelles has been further ascertained by FF-transmission electronic microscopy. The deviations from Cox–Merz rule for the complex dynamic viscosity and the shear viscosity at above the critical shear rate mainly come from the formation of hydrogen bond.

Keywords:

• 3-tetradecyloxy-2-hydroxypropyl trimethylammonium bromide
• rheological property
• self-aggregate

Additional information

Funding

The authors thank the National Natural Science Foundation of China [Grant No. 21473084, 21073081], the Project of Shandong Provincial Education Department [J12LD13] and Liaocheng University Funds [31805] for Young Scientists, the Liaocheng University Teaching Research Project [J201109, G201236, LDSY2014008], the Liaocheng University State Key Laboratory of Crystal Materials [SF2013124, SF2014050, SF2014044] for financial support.