Miscibility phase diagram in blends of syndiotactic polypropylene (sPP) and ethylene-propylene diene terpolymer has been established by means of differential scanning calorimetry, light scattering and optical microscopy. In descending order of temperature, the olefinic blends reveal a complex phase diagram involving a lower critical, solution temperature (LCST), a single phase region followed by a depression of melting transition and a crystal transition (crystallization) of sPP. Below the liquid-solid crystal coexistence Line, phase separation occurs in competition with crystallization of sPP in the blends. Temporal evolution of structure factors and the emergence of phase separated domains in these blends have been investigated by time-resolved light scattering and optical microscopy following several temperature quenches from a single phase into the LCST immiscibility gap. The temporal evolution of structure factors has been analyzed in the context of nonlinear dynamical scaling laws. Vulcanization induced phase separation has been undertaken at various temperatures in the single-phase region. Of particular interest is that the higher the reaction temperature (i.e. the faster the chemical reaction), the smaller the domain size. (C) 2000 Elsevier Science Ltd. All rights reserved.