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Osmotic repulsion force due to adsorbed surfactants
Alexander J Babchin1, Laurier L Schramm
1School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
Colloids and Surfaces. B, Biointerfaces
|November 23, 2011
Summary
Osmotic repulsion forces from overlapping surfactant layers in colloidal dispersions can be substantial. These forces, often overlooked, can significantly impact interfacial interactions.
Area of Science:
- Colloid and Surface Science
- Physical Chemistry
- Materials Science
Background:
- Interaction forces in surfactant-stabilized colloidal dispersions are critical for stability.
- The role of osmotic forces from overlapping adsorbed surfactant monolayers has been rarely discussed.
- Existing models for interfacial forces often neglect osmotic contributions.
Purpose of the Study:
- To develop and apply an advanced method for calculating osmotic repulsion forces in overlapping surfactant monolayers.
- To quantify the magnitude of osmotic forces in real adsorbed surfactant systems.
- To assess the significance of osmotic forces compared to other interfacial forces.
Main Methods:
- Building upon DLVO (Derjaguin–Landau–Verwey–Overbeek) mechanics.
- Adapting concepts from polymer adsorption (Fischer) and osmotic pressure (Langmuir).
- Developing an advanced calculation method for net repulsion force in overlapping monolayers.
- Calculating the first virial term for osmotic pressure.
Main Results:
- An advanced method for calculating net repulsion force in overlapping surfactant monolayers was developed.
- Calculations show disjoining pressure can reach up to 8 MPa under full overlap conditions.
- Osmotic forces are demonstrated to be substantial at close interfacial approach distances.
Conclusions:
- Osmotic forces arising from overlapping adsorbed surfactant monolayers are significant.
- These forces can be comparable to or greater than conventionally considered interaction forces.
- The findings necessitate re-evaluation of interaction force models in colloidal dispersions.
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