Scaling of the Viscoelasticity of Weakly Attractive Particles

The rheological data of weakly attractive colloidal particles are shown to exhibit a surprising scaling behavior as the particle volume fraction, $\phi$, or the strength of the attractive interparticle interaction, $U$, are varied. There is a critical onset of a solid network as either $\phi$ or $U$ increase above critical values. For all solidlike samples, both the frequency-dependent linear viscoelastic moduli, and the strain-rate dependent stress can be scaled onto universal master curves. A model of a solid network interspersed in a background fluid qualitatively accounts for this behavior.