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Published on: April 8, 2011
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Entropy-Regulated Dynamics of Surface Tension: Coupling Langmuir Kinetics with High-Precision Tensiometry
1Department of Chemistry, Al al-Bayt University, Mafraq 25113, Jordan.
The Journal of Physical Chemistry. B
|January 26, 2026
Summary
A new kinetic-thermodynamic model accurately predicts dynamic surface tension for surfactants. This framework simplifies surfactant design for applications like sprays and coatings by revealing general rules for interfacial equilibration.
Area of Science:
- Physical Chemistry
- Surface Science
- Colloid and Interface Science
Background:
- Dynamic surface tension measurements are crucial for understanding interfacial phenomena.
- Existing models often lack generality, hindering the development of predictive design rules for surfactants.
- Interfacial equilibration kinetics are vital for processes like emulsification, sprays, and coatings.
Purpose of the Study:
- To develop a minimal kinetic-thermodynamic framework for dynamic surface tension.
- To establish general design rules for surfactant behavior by coupling adsorption-desorption kinetics with thermodynamics.
- To validate the framework across various surfactant types, concentrations, and temperatures.
Main Methods:
- Developed a framework coupling two-rate adsorption-desorption, Gibbs adsorption, and Arrhenius temperature dependence.
- Validated the model using force tensiometry on ionic (SDS, CTAB) and nonionic (Tween 80) surfactants.
- Conducted experiments across a temperature range (10-80 °C) and surfactant concentrations (sub- to supra-CMC), including uncertainty propagation.
Main Results:
- A single closed-form expression accurately reproduced dynamic surface tension (R² ≥ 0.99).
- Introduced a Damköhler group (Daγ) to partition adsorption-desorption regimes.
- Extracted trends showed adsorption rate (ka) increasing with bulk concentration (Cb) up to CMC, while desorption rate (kd) remained constant; consistent activation energies and entropy generation rates were observed.
Conclusions:
- The developed framework provides a universal method to interpret dynamic surface tension data.
- It enables the mapping of raw data to fundamental kinetic and thermodynamic parameters.
- This facilitates rational selection of surfactant chemistry, concentration, and temperature for optimized interfacial equilibration in industrial applications.
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