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The Paradoxical Behavior of Rough Colloids at Fluid Interfaces
Md Anisur Rahman1, Peter J Beltramo1
1Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States.
ACS Applied Materials & Interfaces
|June 26, 2024
Summary
Surface roughness paradoxically impacts colloidal particle interactions at fluid interfaces. While enhancing deformation in spheres, it weakens it in ellipsoids, offering new avenues for particle surface engineering.
Area of Science:
- Colloid and interface science
- Materials science
- Polymer science
Background:
- Colloidal particles stabilize interfaces via strong adsorption, with contact angle determining behavior.
- Particle surface roughness or shape anisotropy can cause undulated contact lines, leading to quadrupolar interfacial deformation and capillary interactions.
Purpose of the Study:
- To investigate the paradoxical impact of surface roughness on interfacial deformation and capillary interactions of spherical and ellipsoidal polymer colloids.
- To understand how surface roughness influences wetting behavior and capillary forces for different particle shapes.
Main Methods:
- Synthesized spherical and ellipsoidal polymer colloids with controlled surface roughness using seeded emulsion polymerization.
- Measured in situ interfacial deformation around individual colloids at an air-water interface.
- Employed numerical predictions to analyze interfacial deformation and capillary interactions.
Main Results:
- Surface roughness strengthened quadrupolar deformation in spheres, consistent with theory.
- Conversely, surface roughness weakened quadrupolar deformation in ellipsoids.
- Increased roughness led to more hydrophilic particles and decreased apparent contact angles for both shapes.
- Numerical predictions confirmed that decreased wetting explains reduced interfacial deformation in ellipsoids.
Conclusions:
- Surface roughness has a shape-dependent, paradoxical effect on interfacial deformation and capillary interactions.
- Particle surface engineering can tune capillary deformation and interactions by altering wetting behavior and capillary pinning, particularly for asymmetric particles.
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