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Delayed sedimentation of transient gels in colloid-polymer mixtures: dark-field observation, rheology and dynamic light scattering studies

Research output: Contribution to journalArticle

  • Wilson Poon
  • L Starrs
  • S P Meeker
  • A Moussaid
  • R M L Evans
  • P N Pusey
  • M M Robins

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Original languageEnglish
Pages (from-to)143-154
Number of pages12
JournalFaraday Discussions
Issue number112
Publication statusPublished - 1999


The addition of enough non-adsorbing polymer to a hard-sphere suspension causes the particles to aggregate to form a space-filling gel. The integrity of the gel persists for a finite period of time, and then the space-filling structure collapses suddenly to form a denser sediment. This phenomenon of 'delayed sedimentation' is ubiquitous in many weakly-flocculated suspensions. In this work, we observe the processes occurring in the bulk of a colloid-polymer gel using dark-field imaging, and probe the arrangement and dynamics of the particles in the system using two-colour dynamic light scattering. The effect of shear is also studied. A number of physical mechanisms relevant to a comprehensive explanation of delayed sedimentation are proposed and discussed.

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