Linear viscoelastic behavior of aggregated colloidal dispersions

Abstract

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 [Formula Presented] and loss [Formula Presented] moduli over a frequency range of [Formula Presented] The measured [Formula Presented] gradually increases with increasing frequency, while [Formula Presented] 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. © 1997 The American Physical Society.