Department of Physics, Taizhou University, Taizhou 318000, China.
State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, Shanghai 200433, China.
Molecules. 2023 Apr 17;28(8):3536. doi: 10.3390/molecules28083536.
The nanostructures that are self-assembled from block copolymer systems have attracted interest. Generally, it is believed that the dominating stable spherical phase is body-centered cubic (BCC) in linear AB-type block copolymer systems. The question of how to obtain spherical phases with other arrangements, such as the face-centered cubic (FCC) phase, has become a very interesting scientific problem. In this work, the phase behaviors of a symmetric linear BABAB ( = , = ) pentablock copolymer are studied using the self-consistent field theory (SCFT), from which the influence of the relative length of the bridging B-block on the formation of ordered nanostructures is revealed. By calculating the free energy of the candidate ordered phases, we determine that the stability regime of the BCC phase can be replaced by the FCC phase completely by tuning the length ratio of the middle bridging B-block, demonstrating the key role of B-block in stabilizing the spherical packing phase. More interestingly, the unusual phase transitions between the BCC and FCC spherical phases, i.e., BCC → FCC → BCC → FCC → BCC, are observed as the length of the bridging B-block increases. Even though the topology of the phase diagrams is less affected, the phase windows of the several ordered nanostructures are dramatically changed. Specifically, the changing of the bridging B-block can significantly adjust the asymmetrical phase regime of the network phase.
自组装嵌段共聚物体系的纳米结构引起了人们的兴趣。一般认为，在 AB 型线性嵌段共聚物体系中，占主导地位的稳定球形相是体心立方（BCC）。如何获得具有其他排列方式的球形相，如面心立方（FCC）相，已成为一个非常有趣的科学问题。在这项工作中，我们使用自洽场理论（SCFT）研究了对称线性 BABAB（ = ， = ）五嵌段共聚物的相行为，揭示了中间桥接 B 嵌段的相对长度对有序纳米结构形成的影响。通过计算候选有序相的自由能，我们确定通过调整中间桥接 B 嵌段的长度比，可以完全用 FCC 相取代 BCC 相的稳定相区，表明 B 嵌段在稳定球形组装相中起关键作用。更有趣的是，观察到 BCC 和 FCC 球形相之间的异常相转变，即 BCC→FCC→BCC→FCC→BCC，随着桥接 B 嵌段长度的增加而发生。尽管相图的拓扑结构受影响较小，但几种有序纳米结构的相窗口发生了显著变化。具体而言，桥接 B 嵌段的变化可以显著调整网络相的不对称相区。
