探索嵌段共聚物分子结构的设计原理——制备非传统相结构

Block copolymer self-assembly provides a robust platform for the fabrication of ordered nanostructures with the feature size of 5-100 nm which have potential applications in a wide range of fields, and thus it has attracted continuously increasing interest. However, most of researches are focused on the exploration of the self-assembly of a prepared block copolymer to see which structure is formed. In fact, it is more interesting and reasonable to design block copolymer molecules for targeted interesting structures. Therefore, the present proposal aims to exploit a set of rational design principles of architectures of block copolymers for the fabrication of various targeted interesting structures. The pseudo-spectral method of the self-consistent field theory (SCFT) is used to determine the stability region of these targeted structures in the self-assembly of block copolymers with specially designed architectures abiding by the developed design principles. This research is expected to deepen the understanding on the self-assembly of multiblock copolymers. One type of the main targeted structures is the spherical phase, i.e. mesocrystal structures, including binary crystalline phases formed in ABC-type three-component block terpolymers and single crystalline phases formed in AB-type two-component block copolymers. Abiding by the valid design principles and coupling the blending method, this project will design a multitude of block copolymer materials aiming to recast rich crystalline structures (e.g. ionic or metallic alloy crystals) on mesoscale by their self-assemblies, and thus to rationalize the new concept of “Macromolecular Metallurgy”. Then this project will extend the development of design principles to design multiblock copolymers for the fabrication of other interesting non-classical structures. The main task is to demonstrate that the self-assembly of multiblock copolymers can become a panacea that is able to produce all kinds of interesting structures, instead of a Pandora ’s Box.

在该项目中，拟探索嵌段共聚物分子结构的设计原理，为制备多个感兴趣的目标结构设计一系列特定的嵌段共聚物分子，并通过自洽场理论计算预测这些目标结构的稳定相区，理解这些结构稳定存在的机理；从而促进对复杂嵌段共聚物自组装的理解。我们所聚焦的主要结构为球状相，也就是介观晶体结构，包括ABC三组分嵌段共聚物形成的二元球状相、AB两组分嵌段共聚物形成的单元球状相。依据所发展的嵌段共聚物分子结构的设计原理，并结合共混的方法，设计多种嵌段共聚物体系，通过它们的自组装，在介观尺度“重铸”各种晶体结构（例如二元离子或合金晶体结构），完善所提出的“大分子冶金学”的新理念。然后，将设计原理推广到设计制备其他非传统结构的多嵌段共聚物，将多嵌段共聚物自组装变成一个“万能工具”，可以制备各种感兴趣的目标结构。

本项目发展了一系列有效的嵌段共聚物分子结构设计的指导原理，针对非经典纳米有序结构设计了多种嵌段共聚物体系，使用自洽场理论方法计算了它们的相图，预测了这些新结构的稳态相区，揭示了这些非经典结构的形成机理；从而加深了对复杂嵌段共聚物自组装的理解。取得了以下的研究成果：（1）进一步发展了ABC三组分嵌段共聚物分子结构的设计原理，通过自洽场理论计算预测了丰富的非经典相结构，包括类准晶结构。（2）提出了“组合构型熵”概念，设计了两种AB多臂分叉嵌段共聚物分子，在单元介观晶体中实现了“可控桥连嵌段”原理，预测了稳定的四方柱状相、类石墨烯柱状相等非经典相结构，丰富了AB两组分嵌段共聚物分子的设计原理。（3）设计了AB/AB以及ABn/A二元共混体系，均获得了稳定的Frank-Kasper相和Laves相，一方面提出了形成Frank-Kasper相的新途径——两种分子的局域分离扩大了球状相结构的相区，另一方面揭示了Laves相的形成机理——第二种分子的加入使体系可以形成尺寸差异更大的球。（4）所设计的ABAT接枝和ABAB线性嵌段共聚物分子分别形成了稳定的穿孔层和层柱混杂结构，表明分子内相同组分的不同嵌段之间的局域分离为稳定更多非经典相结构提供了新的机理。（5）在ABC三组分嵌段共聚物溶液体系中预测了一系列“行星——卫星”二元胶束结构，成功实现卫星数量的调控，表明嵌段共聚物分子设计的理念可以推广到溶液体系，用于获得非经典胶束结构。相关研究成果在Phys. Rev. Lett.（1篇）、ACS Macro Lett.（4篇）、Macromolecules（6篇）、Prog. Polym. Sci.（1篇）等上发表了20篇标注本项目资助的SCI论文。