Abstract: Unmixing processes of poly (methyl methacrylate) and poly (vinyl acetate)blends were investigated by using light scattering and optical microscope techniques. The results show that there exist self-similarity and fractal behaviour in phase separation processes. In the late stage of phase separation the asymptotic behavior of scaled structure function F(x) is F(x)～x^-6 for large values of x. The fractal dimension of phase structure is about 1.64. These imply that the fractal behaviour of phase structure may result in the scaling feature of structure function.

Key words: phase separation, fractal, scaling, light scattering, structure function