Phase transition processes of benzoylated poly (phenylene oxide) with styrene-butadiene-styrene copolymer blends were studied by using light scattering. The results show that the phase separation at early stage follows the Cahn's theory. In later stage

the phase separation processes were found to give the scaling law on the wave number of the dominant Fourier component of the fluctuation qm(t) and on the maximum scattered intensity Im as given by qm - t-a and Im -tβ. But β<3a