Soft matter under tough pressure:

Dynamical behavior of strained colloidal crystals and glasses

 

Peter Schall, WZI

 

Colloidal suspensions are of great scientific interest, motivated not only by their technological applications but also by their potential use as models to investigate the collective behavior of systems, in which Brownian motion produces an equilibrium state. The colloidal particles -  several ten nanometers to micrometers in size - self-organize into structures (vapor, liquid, glass, crystal) similar to atoms in different phases of condensed matter. Since the particles can be observed optically in real time, colloids can be used to study the dynamics of these phases.

In my post doc at Harvard, I used laser diffraction and confocal microscopy to study the dynamics of strained crystals and glasses comprised of hard-sphere colloidal particles. Confocal microscopy has sufficient resolution to follow the trajectories of the individual particles in time, giving the unique opportunity for studying the dynamics of these suspensions on the particle scale. At the WZI, we will use this technique together with light and X-ray scattering techniques to study colloidal particles suspended in binary liquid mixtures - systems that offer fascinating possibilities to tune the interparticle potential by, for example, varying the temperature. This ability makes these systems versatile and powerful models to investigate gas-liquid or liquid-crystal phase transitions as well as transitions to dynamically arrested states such as glasses or gels. In this talk, I will give some insight into the behavior of hard-sphere crystals and glasses from my previous work and I will present a brief outlook on the planned project at the WZI.