Enthalpy measurements for the formation of salt-induced wormlike micelles using isothermal titration microcalorimetry

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• 作者：Jie Liu^a ; ^b ; Bin Dong^a ; Dezhi Sun^b ; Xilian Wei^b ; Suna Wang^b ; Liqiang Zheng^a ; ^{lqzheng@sdu.edu.cn}
• 关键词：1-Hexadecyl-3-methylimidazolium bromide (C₁₆mimBr) ; Sodium tosylate (NaTos) ; Sodium salicylate (NaSal) ; Wormlike micelle ; Isothermal titration microcalorimetry ; Enthalpy change of wormlike micelle formation
• 刊名：Colloids and Surfaces A: Physicochemical and Engineering Aspects
• 出版年：2011
• 出版时间：5 May 2011
• 年：2011
• 卷：380
• 期：1-3
• 页码：308-313
• 全文大小：514 K

文摘

A simple yet novel method, isothermal titration microcalorimetry (ITC), was employed to determine the enthalpy change of salt-induced wormlike micelle formation. The observed changes in molar enthalpy of 1-hexadecyl-3-methylimidazolium bromide (C₁₆mimBr), sodium tosylate (NaTos) and sodium salicylate (NaSal) in aqueous solutions have been measured. The transformation enthalpy change from spherical micelle to wormlike micelle (ΔH_tra) has been obtained from the simulation method based on the microcalorimetric data. Then the enthalpy change of wormlike micelle formation (ΔH_w) was obtained using a suitable cycle which was closed by the enthalpy change of micelle formation (ΔH_m) and the transformation enthalpy change (ΔH_tra). The value of ΔH_w indicated that the wormlike micelle formation in C₁₆mimBr/NaTos system was exothermic while it was endothermic in C₁₆mimBr/NaSal system. The planar structure of the salicylate anion and the π–π interaction between the salicylate anion and the aromatic headgroup of C₁₆mimBr may attribute to this difference. Moreover, the technique presented here to obtain ΔH_w could be extended to other salt-induced wormlike micelle systems.