SPINODAL DECOMPOSITION OF COLLOIDS IN THE INITIAL AND INTERMEDIATE STAGES

Spinodal decomposition of colloids in the initial and intermediate sta ges is described on the. basis of the Smoluchowski equation. Hydrodyna mic interaction is treated in an approximate way. In the intermediate stage, where a dominant length scale exists, the static structure fact or is found to exhibit universal scaling behavior. The corresponding d ynamic scaling function is derived from the nonlinear equation of moti on for the static structure factor. This scaling function is a much mo re sharply peaked function of the wave vector than the well-known empi rical Furukawa scaling function, which applies to the transition stage where sharp interfaces contribute considerably, giving rise to a Poro d tail at larger wave vectors. The wave vector where the static struct ure factor exhibits a maximum is found to vary with time-in the interm ediate stage-like similar to t(-alpha), where the exponent alpha varie s between 0.2 and 1.1, depending on the relative importance of hydrody namic interaction. Experiments on a microemulsion and binary polymer m elt confirm the predicted scaling behavior. (C) 1996 American Institut e of Physics.