Tuning Colloidal Gel Properties: The Influence of Central and Noncentral Forces

Area of Science:

• Materials Science
• Soft Matter Physics
• Colloid Science

Background:

• Colloidal gels are vital in industry and exhibit reversible solid-to-liquid transitions.
• Surface roughness on particles enhances colloidal gel toughness and self-healing.
• Understanding interparticle forces is key to controlling gel behavior.

Purpose of the Study:

• To quantitatively assess how particle roughness affects adhesive and frictional forces in thermoresponsive colloidal gels.
• To investigate the relationship between interparticle friction and macroscopic gel properties like stability, yielding, and energy storage.
• To explore the role of static interparticle friction, including contributions from chemical roughness.

Main Methods:

• Colloidal probe atomic force microscopy (CP-AFM) to measure forces between individual particles.
• Utilizing thermoresponsive particles to study force variations.
• Conducting experiments with both geometrically and chemically rough particles.

Main Results:

• Increased particle roughness leads to higher static friction, constraining network nodes.
• Higher friction correlates with improved sedimentation stability and a lower percolation threshold.
• Gels with higher friction show a more abrupt elastic-to-plastic transition but greater elastic energy storage capacity.
• Static interparticle friction, regardless of geometric or chemical origin, is critical for macroscopic yielding and recovery.

Conclusions:

• Particle surface roughness, particularly static friction, is a critical parameter controlling colloidal gel mechanical behavior.
• Tailoring interparticle friction through surface modification offers a route to engineer gel properties for specific applications.
• The findings provide fundamental insights into the structure-property relationships in soft materials.