Thermodynamic and Related Properties of Alkyl Cationic Surfactants Based on Dimethyl and Diethyl Ethanol Amines

Abstract

The synthesis and micellar properties of alkyl cationic surfactants based on dimethyl and diethyl ethanol amines have been investigated using conductometric and fluorimetric techniques. The critical micelle concentration (cmc) and degree of counterion binding was determined as a function of temperature. Employing mass action model the relative contribution of hydrophobic and surface energy to Gibbs energy of micellization, degree of counterion binding, and the monomer concentration in the post‐micellar region were evaluated. The aggregation numbers were determined employing fluorimetric techniques. The micellar properties of these series of surfactants were compared with their corresponding trimethyl and triethyl ammonium series to evaluate the effect of substitution of a hydroxyethyl group in place of either a methyl or ethyl group in the head group.

Keywords:

• Cationic surfactants
• micellar properties
• mass action model
• thermodynamics
• aggregation numbers
• micropolarity

Acknowledgments

RP acknowledges the generous support received from NSERC in the form of a discovery grant. AG and MM are grateful for the award of USRA 2002 and 2004 respectively from NSERC.