Effect of aging time and salt on the viscosity behaviour of a Gemini cationic surfactant

ABSTRACT

Rheological properties of micellar solutions of a cationic Gemini surfactant, 2-hydroxypropyl-1,3-bis (dodecyldimethylammonium chloride), are studied as a function of aging time and salt addition. The results show that the self-aggregating behaviour in solution changes as a factor of time, probably due to intermolecular hydrogen bonds. The viscosity of the solution undergoes a series of visible changes so that the solution changes from a flow state to highly viscoelastic state, and finally, to a transparent solid, with a corresponding 4–6-fold increase in zero shear state viscosity. Rheology and freeze fracture transmission electron microscopy (FF-TEM) measurements show rod-like micelles at the beginning, which then change to wormlike micelles, and eventually to a quasi-gel-like network. Addition of an inorganic salt (NaCl) induces salting out, while the addition of an organic salt (NaSal) promotes micellar growth. At a fixed NaSal-to-surfactant molar ratio of 3:5, all solutions show Maxwell fluid behaviour and maximum zero-shear-rate viscosity; these trends can be attributed to the formation of a network structure between the cationic ions of the surfactant and Sal^– as the surfactant concentration increases. Crystal analysis further confirms the presence of structures linked by intermolecular hydrogen bonds.

KEYWORDS:

• Gemini cationic surfactant
• aging effect
• rheological behaviour
• intermolecular hydrogen bond
• wormlike micelle

Acknowledgements

This work was supported by the National Natural Science Foundation of China and Doctoral Fund of Liaocheng University [grant numbers 21473084, 21373106, 318051327, 31805]; Program for Scientific research innovation team in Colleges and universities of Shandong Province, Experimental Technology and Teaching Research Project of Liaocheng University.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China; Doctoral Fund of Liaocheng University [grant number 21473084], [grant number 21373106], [grant number 318051327], [grant number 31805]; Program for Scientific research innovation team in Colleges and universities of Shandong Province; Experimental Technology and Teaching Research Project of Liaocheng University.