Critical Behaviour of Colloidal Interfaces Probed by Gravity

Condensed Matter lunchtime seminar

Critical Behaviour of Colloidal Interfaces Probed by Gravity

  • Event time: 1:00pm
  • Event date: 16th March 2009
  • Speaker: Dirk Aarts (University of Oxford)
  • Location: Room 2511,

Event details

A system of colloidal particles will exhibit a sedimentation gradient when the height of the suspension becomes comparable to the gravitational length of the colloids. In a fluid-fluid phase separated colloid-polymer mixture gradients will be present in both phases, and although only the colloids feel gravity directly, the local polymer density is affected by the local colloid density as well. Here, we show that this has a pronounced effect on the interface behaviour: by increasing the suspension height while keeping the composition of the colloid-polymer mixture constant we effectively scan the phase diagram. Moreover, the effective state point always moves through the critical point at sufficiently large suspension heights. As a result interface fluctuations diverge, and interfacial tension and capillary length diminish as a function of the suspension height. These findings are supported with theoretical calculations.

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

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