Under the mean-field approximation, the free-energy functional of binary mixtures of star-like polymers is derived. With this derived free-energy functional and on the basis of time-dependent Ginzburg- Landau equation, the spinodal decomposition kinetics and the interfacial tension in such system are discussed. It is found that the topological structures of polymer chains do have strong effects on the above mentioned physical properties. Due to the fact that the size of star-like molecule is much smaller than the linear chain for the same molecular weight, the interfacial thickness and the critical correlation length of concentration fluctuation are smaller. It is as expected that the theoretical expressions are reduced to the case of linear chains when the number of arms in a star-like chain equals to 1 or 2.

Key words: PHASE EQUILIBRIUM, PHASE SEPARATION, STATISTICAL MECHANICS, STAR POLYMER