The Effect of Polydispersity and Confinement on the Colloidal Glass Transition

When liquids are rapidly cooled below their freezing point, they can fall out of equilibrium and form disordered solids known as glasses. For systems of colloidal nanoparticles, a glass transition can be induced by increasing the particle density or strength of particle attraction, or by confining the particles. Alternately, for particle systems with low size dispersity, confinement may instead promote crystallization. We use molecular dynamics simulations to investigate these competing scenarios in systems of model colloidal particles confined by two parallel walls. In systems with low and intermediate size dispersity, we observe transitions between alternating crystal structures and phase separation, respectively. As size dispersity is increased, however, we observe the onset of glassy dynamics in the supercooled liquid. Our data sheds light on the interplay between 2D and 3D dynamics in glass formation as well as investigating the connection between phase separation and the colloidal glass transitions.