Thermodynamics Properties of Micellization Process of Surfactants: a Study of Enthalpy-Entropy Compensation Phenomenon

• Main Authors: Chang Hsin-Yi, 張欣怡
• Other Authors: Chen Li-Jen
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/09587337557549936177

碩士 === 國立臺灣大學 === 化學工程學研究所 === 88 === A variety of processes of certain solutes in aqueous solution, such as oxidation-reduction, hydrolysis, protein unfolding, etc., exhibit a linear relationship between the entropy change and the enthalpy change. That is, ΔHmo = ΔHm*+TcΔSmo . This phenomenon is known as enthalpy-entropy compensation. It is well known that when the surfactant concentration in aqueous solution is increased to a certain concentration, known as critical micelle concentration (CMC), the surfactant molecules would automatically aggregate into micelles. The enthalpy (ΔHmo) and entropy (ΔSmo ) of micelle formation are found to obey enthalpy-entropy compensation phenomenon. The purpose of this study is to examine the effect of salts, short-chain alcohols, and co-surfactants on the enthalpy-entropy compensation behavior of micellization process of sodium dodecyl sulfates (SDS) in water. In addition, the degree of dissociation of micelles and the temperature of minimum CMC are also carefully examined. According to the experimental data of CMC as a function of temperature, the and are determined from the Gibbs-Helmholtz equation, and these data are used to find out that the micellization process follows the linear behavior of enthalpy-entropy compensation phenomenon.