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Interaction forces and molecular adhesion between pre-adsorbed poly(ethylene imine) layers.
Ramon Pericet-Camara1, Georg Papastavrou, Sven H Behrens
1Laboratory of Colloid and Surface Chemistry, Department of Inorganic, Analytical, and Applied Chemistry, University of Geneva, Sciences II, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland.
Journal of Colloid and Interface Science
|October 26, 2005
Summary
Interaction forces between poly(ethylene imine) (PEI) layers were studied. Repulsive forces dominate approach, while retraction shows adhesion events influenced by molecular mass and ionic strength, impacting surface interactions.
Area of Science:
- Surface science
- Polymer physics
- Colloid science
Background:
- Pre-adsorbed polymer layers influence surface interactions.
- Poly(ethylene imine) (PEI) is a widely used polyelectrolyte with tunable properties.
- Understanding inter-layer forces is crucial for applications in coatings, adhesives, and biomaterials.
Purpose of the Study:
- To investigate the interaction forces between branched poly(ethylene imine) (PEI) layers of varying molecular masses.
- To elucidate the role of ionic strength and molecular mass on repulsive and attractive forces during surface approach and retraction.
- To characterize the adhesion mechanisms and quantify the work of adhesion for PEI layers.
Main Methods:
- Colloidal probe technique utilizing atomic force microscopy (AFM).
- Systematic variation of PEI molecular mass and ionic strength of the surrounding medium.
- Analysis of force-distance profiles during both approach and retraction phases.
Main Results:
- Repulsive forces dominate during approach due to diffuse layer overlap and electro-steric interactions, with observed surface charge regulation.
- Erratic attractive forces, attributed to molecular adhesion (bridging adhesion), occur during retraction.
- Adhesion events increase with ionic strength; force response exhibits rubber-like extension, with adhesion strength dependent on PEI molecular mass and separation distance.
Conclusions:
- Electro-steric interactions and diffuse layer overlap govern repulsive forces between PEI layers.
- Molecular adhesion, influenced by ionic strength and PEI molecular mass, significantly contributes to retraction forces.
- Work of adhesion increases with ionic strength, highlighting the complex interplay of electrostatic, steric, and molecular bridging effects in PEI layer interactions.