Arrested fluid-fluid phase separation in depletion systems: Implications of the characteristic length on gel formation and rheology

Conrad, J. C.; Wyss, H. M.; Trappe, Véronique; Manley, S.; Miyazaki, K.; Kaufman, L. J.; Schofield, A. B.; Reichman, D. R.; Weitz, D. A.

doi:10.1122/1.3314295

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Journal article

Arrested fluid-fluid phase separation in depletion systems: Implications of the characteristic length on gel formation and rheology

Conrad, J. C. Department of Physics and SEAS, Harvard University, Cambridge, USA - Department of Chemical and Biomolecular Engineering, University of Houston, USA
Wyss, H. M. Department of Physics and SEAS, Harvard University, Cambridge, USA - Eindhoven University of Technology, ICMS & WTB, Eindhoven, the Netherlands
Trappe, Véronique Department of Physics, University of Fribourg, Switzerland
Manley, S. Department of Physics and SEAS, Harvard University, Cambridge, USA - Institute of Physics of Biological Systems, EPFL, Lausanne, Switzerland
Miyazaki, K. Department of Chemistry, Columbia University, New York, USA - Institute of Physics, University of Tsukuba, Japan
Kaufman, L. J. Department of Chemistry, Columbia University, New York, USA
Schofield, A. B. Department of Physics, University of Edinburgh, Edinburgh United Kingdom
Reichman, D. R. Department of Chemistry, Columbia University, New York, USA
Weitz, D. A. Department of Physics and SEAS, Harvard University, Cambridge, USA

12.04.2010

Published in:

Journal of Rheology. - 2010, vol. 54, no. 2, p. 421-438

English We investigate the structural, dynamical, and rheological properties of colloid-polymer mixtures in a volume fraction range of Φ=0.15–0.35. Our systems are density-matched, residual charges are screened, and the polymer-colloid size ratio is ~0.37. For these systems, the transition to kinetically arrested states, including disconnected clusters and gels, coincides with the fluid-fluid phase separation boundary. Structural investigations reveal that the characteristic length, L, of the networks is a strong function of the quench depth: for shallow quenches, L is significantly larger than that obtained for deep quenches. By contrast, L is for a given quench depth almost independent of Φ; this indicates that the strand thickness increases with Φ. The strand thickness determines the linear rheology: the final relaxation time exhibits a strong dependence on Φ, whereas the high frequency modulus does not. We present a simple model based on estimates of the strand breaking time and shear modulus that semiquantitatively describes the observed behavior.

Faculty

Faculté des sciences et de médecine

Department

Département de Physique

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