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

Colloidal gels may experience syneresis, an increase in volume fraction through expulsion of the continuous phase. This poroelastic process occurs when adhesion to the container is weak compared to endogenous stresses which develop during gelation. In this work, we measure the magnitude of syneresis, ΔV/V₀, for gels composed of solid, rubber, and liquid particles. Surprisingly, despite a constant thermoresponsive interparticle potential, gels composed of liquid and elastic particles synerese to a far greater extent. We conclude that this magnitude difference arises from contrasting modes of stress relaxation within the colloidal gel during syneresis either by bending or stretching of interparticle bonds.