线性和非线性聚合物的相分离

LINEAR AND NONLINEAR PHASE DECOMPOSITION IN POLYMERS

分子共混物从20世纪60年代开始,引起很多科学家的兴趣.加工过程中,聚合物相分离过程中的热力学和动力学起了重要的作用,赋予了共混物一定的形貌,提供了很多人们需要的功能.关于聚合物的相分离问题,近年来无论在实验还是在理论上都得到了很大的发展.聚合物相分离的热力学是以Flory-Huggins的平均场理论为基础,动力学以CHC(Cahn-Hilliard-Cook)的线性理论为基础.在本文中,我们对亚稳相分离SD(Spinodal Decomposition)的热力学和动力学都进行了考察.描述了测量二元共混物的浓度涨落的静态散射实验,给出了在二元共混物体系的SD的近期理论计算.首先,从普适的Langevin方程推导CHC理论,从而给出CHC的唯象的平均场理论的微观图象.然后介绍模式耦合计算,从而将SD理论扩展到非线性区域.通过将短期SD分解与高分子共混物的对比揭示了定量计算的本质.最后,讨论了一些近年来在剪切场下相行为的研究以及该领域可能的发展方向.

The area of ＂polymer blends＂ has interested many scientists since the 1960s.This is because the polymer blends provide many special and desirable properties. The thermodynamics of the phase behavior and the kinetics of phase separation/dissolution processes play an important part in these applications. In recent years, lots of advancement have been made in both theories and experiments. The statics part of the phase behavior studies are mostly started from the Flory-Huggins mean-field theory, and the kinetics of phase separation are mostly based on the Cahn-Hilliard-Cook （CHC） linear theory. Many new developments and improvements on theories and new verifications and extensions by experiments have been achieved, including some theoretical and experimental developments in nonlinear phase separation behavior. In this paper, the authors review the scientific development in both the static and kinetic aspects of the spinodal decomposition （SD）. Then, we describe the static scattering experiment,which measures the concentration fluctuations of a binary mixture. After that we present some recent theoretical calculations on the SD of binary polymer system. First, the derivation of CHC theory from generalized Langevin equation is reviewed to provide a microscopic picture for the phenomenological mean-field theory of CHC, Then a mold-coupling calculation was used to extend the SD theory into the nonlinear region. The quantitative nature of the calculation is demonstrated by a comparison with the dissolution study of a polymer blend subjected to SD for a short period, Finally, some recent studies on shear dependence of the phase behavior and possible future potentials and directions in this field have also been discussed.