Viscoelasticity and Structural Aging in Colloidal Gels

I will discuss the behavior of the dynamics of colloidal particles with a weak attractive interparticle interaction that is induced through the addition of polymer to the solvent. I focus on a discussion of aging of the solid gels formed by these colloid-polymer mixtures. They exhibit a delayed collapse induced by gravity and occuring on a characteristic time scale determined by the components of the system. The time evolution of the height of the sediment exhibits an unexpected scaling behavior, suggesting a universal nature to this delayed collapse. I will discuss how the viscoelasticity of the background fluid affects the behavior of the colloidal gel. I complement these measurements of the scaling of the collapse with microscopic investigations of the evolution of the structure of the network using confocal microscopy. These results provide new insight into the origin of this aging behavior.