Effect of aging time and salt on the viscosity behaviour of a Gemini cationic surfactant |
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Authors: | Fanglei Zhang Qian Zhang Chuanhong Han Junhong Zhang Mengjiao Yu |
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Institution: | Shandong Provincial Key Laboratory of Chemical Energy Aging and Novel Cell Technology, College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng, P. R. China |
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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. |
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Keywords: | Gemini cationic surfactant aging effect rheological behaviour intermolecular hydrogen bond wormlike micelle |
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