Bottlebrush block copolymers (BBCPs) exhibit a distinct brush-like topology, which extends their conformations and, consequently, limits chain–chain entanglement in bulk forms and in concentrated solutions. These characteristics make them attractive building blocks to create well-defined nanostructures with large periodicities by self-assembly. However, self-assembly of BBCPs into periodic nanostructures in a dilute solution has rarely been studied. Here, we report the solution self-assembly of amphiphilic BBCPs with poly(ethylene glycol) (PEG) and polystyrene (PS) as pendants attached to a polynorbornene backbone. Similar to the self-assembly of conventional linear block copolymers (BCPs), the BBCPs underwent a morphological transition from spherical micelles to vesicles as their brush ratio, defined by the weight fraction of hydrophilic PEG brushes compared to the weight of the block copolymer brushes (w_PEG), decreased. We found that the BBCPs self-assembled into inverse mesophases when the value of w_PEG was below 7%. In particular, highly symmetric icosahedral cubosomes of BBCPs with internal double diamond lattices were formed when allowed to undergo self-assembly for an extended time period. This condition led us to find that new morphologies from self-assembly of BBCPs in a dilute solution, such as nanotubes and tubular networks, were analogous to the reticulated cylindrical micelles observed from the nonergodic assembly of linear BCPs. Our results suggested that BBCPs could serve a class of macromolecular building blocks to create complex nanostructures with unusual morphologies.

中文翻译：

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在稀溶液中将刷毛嵌段共聚物自组装成三重周期性的纳米结构

洗瓶嵌段共聚物（BBCP）表现出独特的刷状拓扑结构，可扩展其构象，因此可限制散装形式和浓溶液中的链间缠结。这些特性使它们成为有吸引力的构建基块，可以通过自组装来创建具有大周期性的轮廓分明的纳米结构。但是，很少有人研究将BBCPs自组装成稀溶液中的周期性纳米结构。在这里，我们报告了两亲性BBCP的溶液自组装，其中聚（乙二醇）（PEG）和聚苯乙烯（PS）为侧链连接到聚降冰片烯骨架上。与常规线性嵌段共聚物（BCP）的自组装相似，BBCP经历了从球形胶束到囊泡的形态转变，这是它们的刷子比率，w _PEG）降低。我们发现当w _PEG的值低于7％时，BBCPs自组装成反中间相。特别地，当允许其经历长时间的自组装时，形成具有内部双菱形晶格的BBCP的高度对称的二十面体立方体。这种条件使我们发现，在稀溶液中，BBCP的自组装会产生新的形态，例如纳米管和管状网络，类似于线性BCP的非遍历组装观察到的网状圆柱形胶束。我们的研究结果表明，BBCP可以充当一类大分子构件，以创建具有异常形态的复杂纳米结构。