| Abstract
| - The self-association of the tranquilizer chlorpromazine hydrochloride in aqueous solution was studied.Using isothermal titration calorimetry, the critical micelle concentration and solvent−micelle interactionswere evaluated as a function of temperature, ionic strength, and pH. The enthalpy of demicellization,ΔHdemic, was directly measured from the experimental enthalpy values, which showed that the spontaneousdemicellization of chlorpromazine hydrochloride is a highly endothermic process under all experimentalconditions studied. The thermodynamic parameters were subsequently calculated from the temperaturedependent thermograms. At 25 °C, the critical micelle concentration was determined to be 3.2 mM at pH6.5 with a ΔHdemic of 12.5 kJ/mol, a ΔGdemic of 24.3 kJ/mol, and a TΔSdemic of −10.1 kJ/mol. Our resultssuggest that the enthalpy−entropy compensation theory may be applied to these micelles. In addition,using differential scanning calorimetry, a broad endothermic demicellization peak was observed inpostmicelle solutions during heating scans at approximately 45 °C. Cooling scans revealed a very broadpeak centered around 40 °C that corresponds to the heat of micellization.
|
