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Direct force measurements between cellulose surfaces and colloidal silica particles
Igor L Radtchenko1, Georg Papastavrou, Michal Borkovec
1Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Sciences II, 30, Quai Ernest-Ansermet, Geneva 1211, Switzerland.
Biomacromolecules
|November 15, 2005
Summary
Atomic force microscopy revealed repulsive electrostatic forces between silica and cellulose. Cellulose chain desorption from surfaces showed molecular adhesion, driven by non-electrostatic forces like hydrogen bonding.
Area of Science:
- Materials Science
- Surface Chemistry
- Biomaterials
Background:
- Cellulose, a key biopolymer, interacts with various materials.
- Understanding cellulose-silica interactions is crucial for biomaterial development.
- Surface charge and intermolecular forces govern these interactions.
Purpose of the Study:
- To investigate the interaction forces between cellulose layers and colloidal silica particles.
- To quantify electrostatic and non-electrostatic forces during approach and retraction.
- To elucidate the mechanisms of cellulose adsorption and desorption.
Main Methods:
- Direct force measurements using Atomic Force Microscopy (AFM).
- Controlled pH environment to study electrostatic effects.
- Analysis of force-distance curves during probe approach and retraction.
Main Results:
- Repulsive electrostatic forces observed upon approach due to overlapping diffuse layers.
- Estimated cellulose diffuse layer charge density: 0.80 mC/m² (pH 9.5) and 0.21 mC/m² (pH 4).
- Adhesion events during retraction indicated single-chain cellulose desorption forces of 35-42 pN.
Conclusions:
- Cellulose adsorption to surfaces is primarily driven by non-electrostatic forces, likely hydrogen bonding.
- Electrostatic forces contribute to desorption only at high pH when silica is highly charged.
- AFM provides quantitative insights into nanoscale interactions of cellulose with silica.