Glasslike Arrest in Spinodal Decomposition as a Route to Colloidal Gelation (original) (raw)

Abstract

Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich and colloid-poor regions. Gelation results when interconnected colloid-rich regions solidify. We show that this occurs when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition. The characteristic length scale of the gel decreases with increasing quench depth, and the nonergodicity parameter exhibits a pronounced dependence on scattering vector. Mode coupling theory gives a good description of the dynamics, provided we use the full static structure as input.

• Received 14 December 2004

DOI:https://doi.org/10.1103/PhysRevLett.95.238302

©2005 American Physical Society

Authors & Affiliations

S. Manley1,*, H. M. Wyss1, K. Miyazaki2,†, J. C. Conrad1, V. Trappe3, L. J. Kaufman2,†, D. R. Reichman2,†, and D. A. Weitz1

• 1Department of Physics & DEAS, Harvard University, Cambridge, Massachusetts 02138, USA
• 2Department of Chemistry & Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA
• 3Department of Physics, University of Fribourg, CH-1700 Fribourg, Switzerland
• *Present address: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
• †Present address: Department of Chemistry, Columbia University, New York, NY, 10027, USA.

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Images

• Figure 1

Wave vector dependence of the static structure factor for U/kBT=2.46 (dashed line), 2.62 (dashed-dot line), 2.89 (○), 3.06 (△), and 3.85 (◇). The solid line corresponds to the hard-sphere S(q) expected at ϕ=0.25. Inset: U dependence of ΔSm, defined as the difference between the value of S(q) at the nearest-neighbor peak and that at the minimum at qa∼1. The dotted line denotes the point at which the particle-particle position becomes highly correlated. A sharp peak appears concurrently at low q.Reuse & Permissions

• Figure 2

Images obtained by CARS microscopy: U/kBT=2.46 (top left); U/kBT=2.89 (top right); U/kBT=3.06 (bottom left); U/kBT=3.85 (bottom right). The dotted line between the two upper images denotes the boundary beyond which long-lasting, space-filling structures are observed. The scale bars correspond to 10 μm and the circles to π/qc, where qc is obtained from the small angle SLS data. Inset: Schematic phase diagram for colloid-polymer mixtures as polymer concentration and colloid volume fraction are varied, where the glass transition line is marked (GL). Points denote the approximate location of our samples.Reuse & Permissions

• Figure 3

(a) Dynamic structure factor at the q -value of the nearest-neighbor peak for U/kBT=2.46 (dashed line), 2.62 (dashed-dot line), 2.89 (○), 3.06 (△), and 3.85 (◇). To account for the increased viscosity due to the added polymer, the time axis is normalized by the ratio of the viscosity of the polymer solution to that of the solvent, η/η0. (b) Dynamic structure factor for U/kBT=2.89 obtained at qa=1.29 (□), 1.9 (vertical bars), 2.49 (△), 3.03 (○), 3.52 (▽), 4.07 (solid line), and 4.31 (×). The vertical line denotes the f(q,t) values used to approximate the nonergodicity factor fc(q).Reuse & Permissions

• Figure 4

Wave vector dependence of the nonergodicity factor. The symbols are the measured fc(q). From bottom to top the data are for U/kBT=2.89, 3.06, and 3.85. The solid lines are obtained from the MCT calculation using S(q) as input; experimental S(q) at low and high q were smoothed and joined with a spline fit, while at the highest q we use an asymptotic expression for the numerical solution of the PY equation for the Asakura-Oosawa potential, adjusted to match the data. We use values ϕ˜=0.37, 0.52, and 0.50 respectively; the dashed lines are obtained by neglecting the low angle peak.Reuse & Permissions

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