Clustering, wetting and demixing in colloid-microemulsion composites

Condensed Matter lunchtime seminar

Clustering, wetting and demixing in colloid-microemulsion composites

  • Event time: 1:00pm
  • Event date: 26th November 2007
  • Speaker: Danielle Van't Zand (Formerly School of Physics & Astronomy, University of Edinburgh)
  • Location: Room 2511,

Event details

The behaviour of colloids dispersed in a phase-separating microemulsion (micellar solution) are explored using microscopy techniques. It is well known that colloids will cluster approaching a demixing transition of the host solvent; the mechanism is still unresolved. Here a system is used which is intrinsically slow, making experimental studies easier by direct imaging.

On raising the temperature the pure microemulsion separates into micellar liquid and micellar gas phases. The gas phase contains a smaller proportion of the micelles and is less dense. The dynamics are slow, partly because of the size of the micelles. Well before demixing, clustering of the colloids is observed: initially the clusters are irregular in shape and continuously aggregate. When the system gets closer to the phase boundary a wetting layer of the gas phase becomes visible around the colloid aggregates.

Following complete phase separation the colloids prefer the micellar gas phase. The way the separation mechanism is influenced, depends on the microemulsion composition. The colloidal clusters originating prior to demixing cream to the top of the container.

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..

Find out more about Condensed Matter lunchtime seminars.