Temperature Effect on Micelle Formation: Molecular Thermodynamic Model Revisited

Area of Science:

• Physical Chemistry
• Colloid and Surface Chemistry

Background:

• Temperature significantly influences macromolecule aggregation in aqueous solutions.
• The critical micelle concentration (CMC) often exhibits nonmonotonic temperature dependence.

Purpose of the Study:

• To investigate the effect of temperature on surfactant micellization using a molecular thermodynamic model.
• To refine models for predicting CMC and micellar size by modifying key thermodynamic parameters.

Main Methods:

• Employed a molecular thermodynamic model to study surfactant micellization.
• Modified the tail transfer energy to account for head group effects on adjacent methylene groups.
• Adjusted the definition of head size in specific surfactant systems.

Main Results:

• The modified tail transfer energy successfully predicts nonmonotonic CMC behavior with temperature.
• Improved predictions for CMC and micellar size for sodium n-alkyl sulfate, DTAB, and n-alkyl polyoxyethylene.
• Redefining head size in DTAB systems further enhanced prediction accuracy.

Conclusions:

• Tail transfer energy is crucial for accurately modeling temperature-dependent micellization.
• The refined model provides better thermodynamic descriptions of molecular aggregation in bulk and at interfaces.
• This work has direct applications in understanding and modeling surfactant behavior.