THE GLASS-TRANSITION OF COLLOIDAL POLYSTYRENE MICRONETWORK SPHERES - A DYNAMIC LIGHT-SCATTERING STUDY

The collective dynamics of highly concentrated polystyrene micronetwor k spheres of 200 nm diameter as measured by photon correlation spectro scopy (PCS) show a glass transition at phi(g) = 0.64 which is indicate d independent of any theory through specific changes in the intensity fluctuation pattern. On the 'liquid' side, the same qualitative featur es as known for molecular liquids or colloidal suspensions close to th e glass transition are found. A two-step decay of the density fluctuat ions is observed with PCS which can be quantitatively interpreted by m ode coupling theory (MCT) with a critical volume fraction phi(c) of 0. 64, and the analogon of the time-temperature superposition principle h olds. However, above phi(c), the density fluctuations do not decay to a finite plateau indicating the freezing of the alpha-process, but sho w a remnant decay at long times, leading to a dynamical behaviour that cannot be treated within the idealized MCT.