The inherent statistical heterogeneities associated with chain length, composition, and architecture of synthetic block copolymers compromise the quantitative interpretation of their self-assembly process. This study scrutinizes the contribution of molecular architecture on phase behaviors using discrete ABA triblock copolymers with precise chemical structure and uniform chain length. A group of discrete triblock copolymers with varying composition and symmetry were modularly synthesized through a combination of iterative growth methods and efficient coupling reactions. The symmetric ABA triblock copolymers self-assemble into long-range ordered structures with expanded domain spacings and enhanced phase stability, compared with the diblock counterparts snipped at the middle point. By tuning the relative chain length of two end blocks, the molecular asymmetry reduces the packing frustration, and thus increases the order-to-disorder transition temperature and enlarges the domain sizes. This study would serve as a quantitative model system to correlate the experimental observations with the theoretical assessments and to provide quantitative understandings for the relationship between molecular architecture and self-assembly.

中文翻译：

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分子结构和对称性对自组装的影响：使用离散 ABA 三嵌段共聚物进行定量研究

与合成嵌段共聚物的链长、组成和结构相关的固有统计异质性损害了对其自组装过程的定量解释。本研究使用具有精确化学结构和均匀链长的离散 ABA 三嵌段共聚物仔细检查分子结构对相行为的贡献。通过迭代生长方法和高效偶联反应相结合，模块化合成了一组具有不同组成和对称性的离散三嵌段共聚物。与在中间点剪断的二嵌段对应物相比，对称的 ABA 三嵌段共聚物自组装成具有扩大的域间距和增强的相稳定性的长程有序结构。通过调整两个端块的相对链长，分子不对称减少了堆积挫折，从而提高了有序到无序的转变温度并扩大了域尺寸。本研究将作为一个定量模型系统，将实验观察与理论评估联系起来，并为分子结构和自组装之间的关系提供定量理解。