Thermally-induced Transition in Aqueous Solution of Cationic Surfactant Containing Aromatic Ring |
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| Authors: | Endoh Kei-ichi Suga H Fukada H |
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| Institution: | (1) Research Institute for Science and Technology, Kinki University, Kowakae, Higashi-Osaka 577-8502, Japan;(2) Laboratory of Biophysical Chemistry, College of Agriculture, University of Osaka Prefecture, Sakai, Osaka 599-8231, Japan |
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| Abstract: | Heat capacities of aqueous solutions of cetyltrimethylammonium (CTA) salicylate, of CTA m-hydroxybenzoate and of CTA p-hydroxybenzoate were measured using a scanning microcalorimeter. Only the salicylate solution exhibited heat-capacity anomaly around 330 K, depending on the heating rate. The transition enthalpy was 3.5±0.2 kJ mol–1, which was similar to that observed in solution of 1:1 intermolecular compound between CTA bromide (CTAB) and o-iodophenol (OIPh). The enthalpy of formation  Hf of the 1:1 intermolecular compound from CTAB and OIPh was determined by measuring the enthalpies of solution of the relevant crystals into ethanol. Positive value fH=3.0±0.3 kJ mol–1 was explained from a large difference between the heat capacities of the 1:1 compound and 1:1 mixture of the component crystals.This revised version was published online in November 2005 with corrections to the Cover Date. |
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| Keywords: | enthalpy of formation intermolecular compound rod-like micelles surfactant with additive thermal transition |
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