Colloidal dispersions

A researcher at Bath University has been awarded £297,000 by the Engineering & Physical Sciences Research Council to study the effects of adding nanoparticles to colloidal dispersions.

Colloidal dispersions are a type of fluid in which ‘colloid’ particles of micron size are dispersed in a liquid solvent. Examples arise in a host of everyday household products including detergents, cosmetics and paints, as well as many foodstuffs like mayonnaise and ice cream. They also find technological applications, for instance as lubricants and drug delivery systems.

One issue is key to the material properties of all such systems, namely the stability of the suspension, or more generally its ‘phase behaviour’. Specifically, researchers would like to be able to predict whether under prescribed external conditions of, for example, temperature and pressure, a certain type of colloidal dispersion remains stable - that is the particles are evenly dispersed throughout the solvent - or instead separate off to form a dense ‘phase’ or aggregate. If a dense phase does form, they would like to be able to predict and even control its structural properties.

Using the grant money, Dr Nigel Wilding of Bath University’s Department of Physics plans to employ a computer simulation method jointly developed by himself and colleagues at the University of Illinois at Urbana-Champaignto to study the properties of colloidal dispersions to which much smaller ‘nanoparticles’ have been added.

Such additives are known to dramatically change the physical properties of a dispersion, including the tendency of the colloid particles to phase separate. This happens because the additive modifies the effective interaction between colloids. However, a complete understanding of just how this happens, and the generic consequences for phase behaviour, is presently lacking.