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Can the Thermophoretic Mobility of Uncharged Colloids Be Predicted?
Konstantin I Morozov1, Werner Köhler2
1Department of Chemical Engineering, Technion - Israel Institute of Technology, Haifa 32000, Israel.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 16, 2022
Summary
Nonionic colloids exhibit thermophoretic motion driven by solvent-colloid interactions, leading to a drift towards colder regions. This study predicts thermophoretic velocities and offers a method to determine solute-solvent interaction constants.
Area of Science:
- Colloid Science
- Thermodynamics
- Fluid Dynamics
Background:
- Thermophoresis describes particle movement in temperature gradients.
- Solvent-colloid interactions create microconvective flows influencing particle motion.
- Understanding these interactions is key for predicting colloid behavior.
Purpose of the Study:
- To predict the thermophoretic velocities of nonionic colloids.
- To investigate the influence of solvent-colloid dispersion interactions on thermophoresis.
- To establish a link between thermophoretic mobility and the Hamaker constant.
Main Methods:
- Augmenting Boussinesq convection equations with specific boundary conditions.
- Modeling microconvective motion near colloids.
- Calculating thermophoretic mobilities for various colloid types.
Main Results:
- Thermophoretic motion is driven by an attractive "gravity" field from solvent-colloid interactions.
- Mobilities depend on bulk properties and the Hamaker constant, with weak size dependence.
- A universal mobility value is observed for strongly asymmetrical mixtures.
Conclusions:
- This work provides the first prediction of thermophoretic velocities for uncharged colloids.
- The findings enable experimental determination of the Hamaker constant using thermophoresis data.
- The study elucidates the fundamental mechanisms governing thermophoresis in colloidal systems.
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