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Nonlinear dynamics in micellar surfactant solutions. I. Kinetics
Joshua A Mysona1, Alon V McCormick1, David C Morse1
1Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. SE, Minneapolis, Minnesota 55455, USA.
Physical Review. E
|April 16, 2022
Summary
This study develops models for surfactant solutions, explaining how micelle concentration changes. It focuses on kinetics in homogeneous solutions, crucial for understanding interfacial adsorption processes.
Area of Science:
- Physical Chemistry
- Chemical Engineering
- Materials Science
Background:
- Understanding micelle formation and dynamics is key in surfactant science.
- Existing models often struggle with large deviations from equilibrium and complex kinetic processes.
Purpose of the Study:
- To develop robust, reduced models for kinetic and transport phenomena in micelle-forming surfactant solutions.
- To describe both homogeneous and inhomogeneous systems using differential equations for key parameters like unimer and micelle concentrations.
- To model systems exhibiting large deviations from equilibrium, including suppressed unimer concentrations.
Main Methods:
- Developed a general nonlinear theory for fast stepwise processes.
- Integrated this with existing nonlinear theories for slow association and dissociation.
- Analyzed kinetics under both stepwise reaction and fission-fusion mechanisms.
- Investigated dependencies of micelle lifetime and relaxation time on surfactant concentration.
Main Results:
- Constructed differential equation models for unimer concentration (c1), micelle number concentration (cm), and average micelle aggregation number (q).
- Successfully modeled systems with significant suppression of c1 below the critical micelle concentration, leading to rapid micelle shrinkage.
- Analyzed the impact of different kinetic mechanisms (stepwise vs. fission-fusion) on micelle dynamics and relaxation times.
Conclusions:
- The developed models provide a robust framework for studying complex kinetic phenomena in surfactant solutions.
- The theory facilitates the analysis of large deviations from equilibrium, relevant for interfacial processes.
- Understanding these dynamics is critical for applications involving surfactant self-assembly and interfacial behavior.
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