Polymer-enforced crystallization of a eutectic binary hard sphere mixture

Abstract

We prepared a buoyancy matched binary mixture of polydisperse polystyrene microgel spheres of size ratio Γ = 0.785 at a volume fraction of Φ = 0.567 just below the kinetic glass transition. In line with theoretical expectations, a eutectic phase behaviour was observed, but only a minor fraction of the samples crystallized at all. By adding a short non-adsorbing polymer we enforce inter-species fractionation into coexisting pure component crystals, which in turn also shows signs of intra-species fractionation. We show that in formerly inaccessible regions of the phase diagram binary hard sphere physics are made observable using attractive hard spheres.