The viscoelastic behavior of a depletion-flocculated dispersion of colloidal spheres is investigated at different volume fractions of the spheres, using a controlled stress and a dynamic rheometer. Combining the results, we obtain the storage $G^{\prime }$ and loss $G^{\prime \prime }$ moduli over a frequency range of $0.02<\mathrm{}\omega <200\mathrm{}\mathrm{r}\mathrm{a}\mathrm{d}/\mathrm{s}.$ The measured $G^{\prime }$ gradually increases with increasing frequency, while $G^{\prime \prime }$ almost remains constant, indicating a broad spectrum of relaxation times. To describe and explain the observed behavior of the moduli as a function of frequency and volume fraction in terms of microscopic parameters, a microrheological model based on the fractal concept is proposed. Comparing experimental results with model calculations, we find a good agreement between the two, with physically plausible parameter values.

• Received 16 January 1997

DOI:https://doi.org/10.1103/PhysRevE.56.5726