Thesis subject

BSc & MSc - Colloidal Cocktails: The glass transition in binary mixtures of charged colloids

A glass has the structural characteristics of a fluid, with an unordered and amorphous structure, yet it behaves as a solid. The transition from a freely-flowing fluid to solid-like glass, without any change in the microstructure of the material, remains one of the ultimate unsolved problems in solid state physics.

Left: Highly charged and monodisperse colloids form crystals, shown in a confocal microscopy image and a computer-generated rendering of its 3D structure. Right: By contrast, mixtures of charged colloids of two different sizes (red = large particles, green = small particles) form amorphous phases, called glasses.
Left: Highly charged and monodisperse colloids form crystals, shown in a confocal microscopy image and a computer-generated rendering of its 3D structure. Right: By contrast, mixtures of charged colloids of two different sizes (red = large particles, green = small particles) form amorphous phases, called glasses.

Colloids form an interesting platform to study this mysterious form of matter; their relatively large size and thus slow dynamics allows the use of light scattering, rheology and microscopy to study the glass transition under ambient conditions. Monodisperse colloidal particles ultimately want to crystallize (see figure), which complicates the study of their glass transition. When mixing two different sizes of colloids (see figure) the formation of crystals is hindered so strongly, that glasses are always formed. These so-called binary colloidal mixtures thus form a very promising experimental system to investigate this fascinating state of matter. In this project we will explore these exciting systems and dive into the study of their glass transition.

As there is no structural difference between a glass and a liquid, we will investigate the dynamic fingerprints of glassification. This will be accomplished using a combination of high-end experimental methods such as contrast-variation Dynamic Light Scattering, confocal microscopy-based microrheology and classical bulk rheological measurements. Your work will shed new light on the enigma that is the glass transition.

Experimental techniques:

  • Dynamic and static light scattering
  • Rheology
  • Confocal microscopy-based microrheology
  • Optional: colloid synthesis