Colloidal polystyrene micronetwork spheres — a new mesoscopic model of the glass transition in simple liquids

The collective and single particle dynamics of highly concentrated polystyrene micronetwork spheres of 200 nm diameter as measured by photon correlation spectroscopy (PCS) and forced Rayleigh scattering (FRS), respectively, show the same qualitative features as known for molecular liquids or colloidal suspensions close to the glass transition. A two step decay of the density fluctuations is observed with PCS, which can be quantitatively interpreted by mode coupling theory with a critical volume fraction ϕc of 0.64. At the same volume fraction a glass transition is indicated independent of any theory through specific changes in the intensity fluctuation pattern. The long time self-diffusion coefficient, as determined by FRS, decreases over about three orders of magnitude in a small volume fraction interval between 0.55 and 0.68. However, traces of ergodicity restoring structure relaxation processes are found even beyond ϕc = ϕg.