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arXiv · 0710.5459

High-bandwidth viscoelastic properties of aging colloidal glasses and gels

S. Jabbari-Farouji·M. Atakhorram·D. Mizuno·E. Eiser·G. H. Wegdam·F. C. MacKintosh·Daniel Bonn·C. F. Schmidt
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Abstract

We report measurements of the frequency-dependent shear moduli of aging colloidal systems that evolve from a purely low-viscosity liquid to a predominantly elastic glass or gel. Using microrheology, we measure the local complex shear modulus $G^{*}(ω)$ over a very wide range of frequencies (1 Hz- 100 kHz). The combined use of one- and two-particle microrheology allows us to differentiate between colloidal glasses and gels - the glass is homogenous, whereas the colloidal gel shows a considerable degree of heterogeneity on length scales larger than 0.5 micrometer. Despite this characteristic difference, both systems exhibit similar rheological behavior which evolve in time with aging, showing a crossover from a single power-law frequency dependence of the viscoelastic modulus to a sum of two power laws. The crossover occurs at a time $t_{0}$, which defines a mechanical transition point. We found that the data acquired during the aging of different samples can be collapsed onto a single master curve by scaling the aging time with $t_{0}$. This raises questions about the prior interpretation of two power laws in terms of a superposition of an elastic network embedded in a viscoelastic background. Keywords: Aging, colloidal glass, passive microrheology

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S. Jabbari-Farouji, M. Atakhorram, D. Mizuno, E. Eiser, G. H. Wegdam, F. C. MacKintosh, Daniel Bonn, C. F. Schmidt. 2007-10-29. High-bandwidth viscoelastic properties of aging colloidal glasses and gels. https://doi.org/10.1103/physreve.78.061402

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