MEASUREMENT OF THE SELF-INTERMEDIATE SCATTERING FUNCTION OF SUSPENSIONS OF HARD SPHERICAL-PARTICLES NEAR THE GLASS-TRANSITION

Dynamic light-scattering measurements are reported for suspensions at concentrations in the vicinity of the glass transition. In a mixture o f identically sized but optically different particles having hard-sphe re-like interactions, we project out the incoherent (or self-) interme diate scattering functions by adjusting the refractive index of the su spending Liquid until scattering from the structure is suppressed. Due to polydispersity, crystallization is sufficiently slow so that good estimates of ensemble-averaged quantities can be measured for the meta stable fluid states. Crystallization of the suspensions is still explo ited, however, to set the volume fraction scale in terms of effective hard spheres and to eliminate (coherent) scattering from the structure . The glass-transition volume fraction is identified by the value wher e large-scale particle motion ceases. The nonequilibrium nature of the glass state is evidenced by the dependence on the waiting time of the long time decay of the relaxation functions. The self-intermediate sc attering functions show negligible deviation from Gaussian behavior up to the onset of large-scale diffusion in the fluid or the onset of wa iting time effects in the glass. [S1063-651X(98)12810-6].