Kinetic Pathways to Gelation and Effects of Flow-Induced Structuring in Depletion Gels

Area of Science:

• Colloid and Polymer Science
• Materials Science
• Soft Matter Physics

Background:

• Colloidal gels are ubiquitous in nature and industry.
• Understanding gelation kinetics and flow effects is crucial for material design.
• Traditional mixing methods can introduce flow history, complicating gel structure analysis.

Purpose of the Study:

• To investigate the kinetic pathways of gelation in depletion flocculated gels.
• To examine the impact of flow-induced restructuring on gel microstructure.
• To compare gel formation under quiescent conditions versus flow-induced preparation.

Main Methods:

• Experimental techniques including time-resolved confocal microscopy.
• Computer simulations incorporating long-range hydrodynamic interactions.
• Controlled preparation of gels by salt diffusion and high-rate preshear.

Main Results:

• Quiescent gelation leads to reduced heterogeneity and strand size with increased attraction strength.
• Shear flow significantly impacts gel structure, causing fluidization or heterogeneous aggregate formation.
• Gel heterogeneity is controlled by the balance between flow strength and inter-colloid attraction.

Conclusions:

• Preparation protocols critically influence colloidal gel structure and properties.
• Kinetic aggregation pathways can dominate over attraction effects in determining gel microstructure.
• This work provides a framework for optimizing gel preparation and achieving structural reproducibility.