星型高分子共混体系的相平衡、相分离和相界面的统计力学理论

在平均场近似下求得了星型高分子共混体系的混合自由能及其相分离动力学方程。本文的理论结果表明,型高分子共混体系与线型高分子共混体系相比具有更快的相分离速度。而且,因其相界面张力较低,体系较易形成更多的相界面,浓度涨落的临界波矢也更大。除此之外,由于在相同分子量的条件下星型高分子的尺寸要小,因此其相界面更窄,当星型高分子的臂数为1或2时,所有结果均合理地还原到熟知的线型高分子共混体系的结果。因此,本文的结果具有更大的普遍性。

The statistical thermodynamics theory of the phase equilibrium, spinodal decomposition kinetics and interfaces in star-like polymeric binary mixtures

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.