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

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

Research output: Contribution to journalArticlepeer-review

Abstract

We investigate the structural, dynamical, and rheological properties of colloid-polymer mixtures in a volume fraction range of phi=0.15-0.35. Our systems are density-matched, residual charges are screened, and the polymer-colloid size ratio is similar to 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 phi; this indicates that the strand thickness increases with phi. The strand thickness determines the linear rheology: the final relaxation time exhibits a strong dependence on phi, 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.

Original languageEnglish
Pages (from-to)421-438
Number of pages18
JournalJournal of rheology
Volume54
Issue number2
DOIs
Publication statusPublished - 2010

Keywords

  • colloids
  • phase separation
  • polymer blends
  • polymer gels
  • quenching (thermal)
  • rheology
  • shear modulus
  • COLLOID-POLYMER MIXTURES
  • EQUILIBRIUM CLUSTER FORMATION
  • STOKES-RAMAN SCATTERING
  • SPINODAL DECOMPOSITION
  • NONUNIFORM SYSTEM
  • MODEL SYSTEM
  • FREE ENERGY
  • SUSPENSIONS
  • BEHAVIOR
  • GELATION

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