KINETICS OF PHASE-SEPARATION IN BINARY-MIXTURES OF POLYSTYRENE AND POLY(VINYL METHYL-ETHER) AS STUDIED BY FLUORESCENCE EMISSION OF LABELED POLYSTYRENE

The initial stages of phase separation in binary mixtures of polystyrene and poly(vinyl methylether) have been examined by using a fluorescence emission technique. The experiments were performed on a series of mixtures covering the entire composition range. Thus, both the spinodal decomposition mechanism in the unstable one-phase region and the nucleation and growth mechanism in the metastable regions were investigated. The rates of phase separation are shown to present a logarithmic dependence on time. Their initial values vary in accordance with the driving forces predicted by the relevant theories. Two polystyrene samples of different molecular weight (MBAR(w) = 35 000 and 233 000) were used in order to check the influences of blend viscosity and phase separation temperature on the kinetics of the processes. In the nucleation and growth regime, chain mobility is an important factor, and the observed behavior is quite well described by assuming the validity of the Williams-Landel-Ferry (WLF) equation.