嵌段共聚物增容机制的理论研究：胶束的形成与破裂

In this project, we propose to investigate the mechanism of compatibilization of A/B polymer blends using A-B diblock copolymers by focusing on the formation and rupture of the diblock copolymer micelles that are the necessary intermediates in the process. First, we study the equilibrium behavior of A-B self-assembly in a single homopolymer A and in an A/B blend. The structure and thermodynamics of micelles (in single component A) or swollen micelles (in A/B blend) will be examined using the grand canonical ensemble formulation of the self-consistent field theory. In particular, by studying the free energy of formation, we establish a rigorous determination of the critical micelle concentration (CMC). With this equilibrium information as a guide, we then consider the kinetic process of adding homopolymer B to a solution with A-B diblock copolymer micelles in homopolymer A. Specifically, we will consider how the A-B diblock copolymer micelles fuse with a droplet of B homopolymer resulting in A-B diblock copolymers adsorbed at the interface between homopolymers A and B. Since this step is likely to involve an activation barrier, we will develop the string method for this A-B/A/B system to identify the minimum free energy path for this process. Experiments will be performed in conjunction with the theoretical work. We expect that the theories developed in this work together with the experimental results will provide the necessary mechanistic understanding of compatibilization of A/B polymer blends using A-B diblock copolymers and serve as useful guide for industrial processing of such systems.

本项目中我们将从胶束的形成与破裂入手研究嵌段共聚物在共混物体系中的增容机制。 首先研究嵌段共聚物在单一均聚物A以及A/B共混物中的自组装行为，发展巨正则系综下的自洽场理论，研究胶束（在单一均聚物A中）或溶胀胶束（在A/B共混物中）的结构以及热力学性质，考虑多根高分子链形成胶束所需要的能量，准确的计算临界胶束浓度（CMC）。其次加入另一种均聚物B，研究含有胶束的共混物体系的相分离动力学，明确胶束是如何与B均聚物融合并且迁移至均聚物A/B两相的界面处，考察胶束稳定性对这一过程的影响；考虑到这一过程涉及到能垒的翻越，我们将发展研究不同稳态结构之间演化的弦方法(String Method)，得到其演化的自由能极小路径。最后，结合理论的实验工作也将会同时展开。 所发展的理论方法以及实验结果将有助于理解嵌段共聚物的增容机制、寻找最佳实验条件以及加工方法，为实际的生产加工提供理论依据。

本项目主要运用自洽场理论，研究胶束的形成与破裂，从而明确嵌段共聚物的增容机制，主要取得了如下的研究成果：（1）在胶束形成方面，考虑局部涨落的体系研究了胶束的形成，准确计算了单个胶束的生成自由能，发展了精确得到临界胶束浓度方法；（2）对Flory- Huggins理论在稀溶液下进行修正，并得到了聚合物共混物的Coil-to-Globule转变；（3）发展了研究星型多臂嵌段共聚物(AB)f的自洽场方法，并且研究其在体相及受限下的自组装。项目的研究成果在Science子刊Science Advances（一篇）, Nanoscale（一篇）, Langmuir（两篇）以及高分子学报（一篇）等上发表了5篇SCI论文。