Sol-gel transition of concentrated colloidal suspensions

Diffusing-wave spectroscopy (DWS) was used to follow the sol-gel transition of concentrated colloidal suspensions; We present a new technique based on a sandwich of two scattering cells aimed to overcome the problem of nonerg odicity in DWS of solidlike systems. Using this technique we obtain quantit ative information about the microscopic dynamics all the way from an aggreg ating suspension to the final gel, thereby covering the whole sol-gel trans ition. At the gel point a dramatic change of the particle dynamics from dif fusion to a subdiffusive arrested motion is observed. A critical-power-law behavior is found for the time evolution of the maximum mean square displac ement delta (2) probed by a single particle in the gel.