Thermodynamics of Sodium Dodecyl Sulfate (SDS) Micellization: An undergraduate Laboratory Experiment

MARCOLONGO, J.P.; MIRENDA, M.

JOURNAL OF CHEMICAL EDUCATION

AMER CHEMICAL SOC

Año: 2011 vol. 88 p. 629 - 633

0021-9584

We present an undergraduate laboratory experiment that allows a thermodynamic characterization of micelle formation of sodium dodecyl sulfate, SDS, in aqueous solutions. The Critical Micelle Concentration, CMC, and the degree of micelle ionization, , are obtained at different temperatures by conductimetry. The molar standard free energy ( ), enthalpy ( ) and entropy ( ) for the micellization process are calculated using the CMC, , and their temperature dependences within the framework of a simplified model - the closed association model - that assumes equilibrium between free surfactant monomers and monodispersed micelles. Based on hydration phenomena of surfactant molecules, a physicochemical discussion of the results is also proposed.