COLLOIDAL POLYSTYRENE MICRONETWORK SPHERES - A NEW MESOSCOPIC MODEL OF THE GLASS-TRANSITION IN SIMPLE LIQUIDS

The collective and single particle dynamics of highly concentrated pol ystyrene 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 molecula r liquids or colloidal suspensions close to the glass transition. A tw o step decay of the density fluctuations is observed with PCS, which c an be quantitatively interpreted by mode coupling theory with a critic al volume fraction phi(c) of 0.64. At the same volume fraction a glass transition is indicated independent of any theory through specific ch anges in the intensity fluctuation pattern. The long time self-diffusi on coefficient, as determined by FRS, decreases over about three order s of magnitude in a small volume fraction interval between 0.55 and 0. 68. However, traces of ergodicity restoring structure relaxation proce sses are found even beyond phi(c) = phi(g).