Effect of Ethylene Glycol on the Thermodynamic and Micellar Properties of Tween 40, 60, and 80

The self‐aggregation of Tween 40, Tween 60, and Tween 80 in ethylene glycol‐water mixture was investigated using surface tension, density, and fluorescence measurements. The mixtures were observed to appreciably affect the critical micelle concentration (cmc) of the surfactants and their aggregation numbers. In order to evaluate the influence of the solvent mixture, the difference in the Gibbs energy of micellization of Tween 40, Tween 60, and Tween 80 between water and binary mixtures were determined. The ability of ethylene glycol acting as a structure breaker and its interaction with the surfactant hydrophilic group are the controlling factors for the micellization of the surfactants in the mixture. The surface activity of the surfactants decreases with increasing concentration of ethylene glycol in the mixture. Micellar micropolarity was determined using the fluorescence method. The results indicate the participation by ethylene glycol in the micellar solvation layer.

Keywords:

• thermodynamics of micellization
• tweens
• head group area
• ethylene glycol‐water mixtures
• fluorescence

Acknowledgments

RP acknowledges the operating grant from Natural Sciences and Engineering Research Council (NSERC). SCB is grateful to Jadavpur University, Kolkata, India for the leave of absence and to St. Francis Xavier University for the James Chair Visiting Research Professorship. KG acknowledges USRA award from NSERC (2004).