Syneresis of Colloidal Gels: Endogenous Stress and Interfacial Mobility Drive Compaction

Area of Science:

• Materials Science
• Soft Matter Physics
• Colloid Science

Background:

• Colloidal gels can undergo syneresis, a process where the continuous phase is expelled, increasing the gel's volume fraction.
• Syneresis is a poroelastic phenomenon driven by internal stresses exceeding adhesion to the container during gelation.

Purpose of the Study:

• To quantify the extent of syneresis in colloidal gels composed of different particle types (solid, rubber, liquid).
• To investigate the influence of particle composition on the magnitude of syneresis, particularly under constant thermoresponsive interparticle potentials.

Main Methods:

• Experimental measurement of syneresis magnitude (ΔV/V₀) in colloidal gels.
• Systematic variation of particle composition (solid, rubber, liquid) while maintaining a constant interparticle potential.

Main Results:

• Gels composed of liquid and elastic particles exhibited significantly greater syneresis compared to gels made of solid particles.
• This difference in syneresis magnitude was observed despite a constant thermoresponsive interparticle potential across all gel types.

Conclusions:

• The contrasting syneresis magnitudes are attributed to different stress relaxation mechanisms within the colloidal gel.
• Liquid and elastic particle gels likely relax stress through bond stretching, while solid particle gels may involve bond bending, leading to varied syneresis.