建筑半柔性嵌段共聚物的异常自组装
Anomalous Self-assembly of Architecturally Semiflexible Block Copolymers
摘要：
嵌段共聚物自组装是一个基本的过程，其中不相容的嵌段自发地形成有组织的微结构，具有广泛的实际应用。传统的理解是，域间距受到聚合物主链的轮廓长度的限制。在这里，使用分子设计，化学合成，小/广角X-射线散射，透射电子显微镜和电子断层扫描的组合，我们发现，这种分子图片不适用于建筑半柔性嵌段共聚物。对于强分离的线性-半柔性瓶刷-线性三嵌段共聚物，瓶刷结构域的尺寸可以是瓶刷骨架轮廓长度的两倍。这种异常自组装的机制可能是不相容嵌段之间的界面排斥力足够大，以将一部分线性末端嵌段拉入瓶刷结构域。这有效地增加了瓶刷域的大小。此外，半柔性瓶刷拓宽了与端块$f_C^{SFB}\in(0.10,>0.40)$的体积分数相关的圆柱体形态的范围。这个窗口比柔性线性嵌段共聚物，$f_C^{F} \in(0.14,0.35)$，和最近的自洽场论预测的相同的化学和分子结构的线性瓶刷嵌段共聚物宽得多。我们的实验结果揭示了以前未被认识到的结构复杂的嵌段共聚物的自组装机制。
英文摘要：
Block copolymer self-assembly is a fundamental process in which incompatible blocks spontaneously form organized microstructures with broad practical applications. Classical understanding is that the domain spacing is limited by the contour length of the polymer backbone. Here, using a combination of molecular design, chemical synthesis, small/wide-angle X-ray scattering, transmission electron microscopy, and electron tomography, we discover that this molecular picture does not hold for architecturally semiflexible block copolymers. For strongly segregated linear-semiflexible bottlebrush-linear triblock copolymers, the size of the bottlebrush domain can be twice the bottlebrush backbone contour length. The mechanism of such anomalous self-assembly likely is that the interfacial repulsion between the incompatible blocks is large enough to pull a part of the linear end-blocks into the bottlebrush domain. This effectively increases the bottlebrush domain size. Moreover, the semiflexible bottlebrush widens the regime for cylinder morphology that is associated with the volume fraction of the end blocks $f_C^{SFB}\in(0.10,>0.40)$. This window is much wider than that for flexible linear block copolymers, $f_C^{F} \in(0.14,0.35)$, and that predicted by recent self-consistent field theory for linear-bottlebrush block copolymers of the same chemistry and molecular architecture. Our experimental findings reveal previously unrecognized mechanisms for the self-assembly of architecturally complex block copolymers.
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