Gröschel Tina I, Wong Chin Ken, Haataja Johannes S, Dias Marcelo A, Gröschel Andre H
Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany.
Physical Chemistry and Center for Soft Nanoscience (SoN), University of Münster, 48149 Münster, Germany.
ACS Nano. 2020 Apr 28;14(4):4829-4838. doi: 10.1021/acsnano.0c00718. Epub 2020 Apr 8.
Topology and defects are of fundamental importance for ordered structures on all length scales. Despite extensive research on block copolymer self-assembly in solution, knowledge about topological defects and their effect on nanostructure formation has remained limited. Here, we report on the self-assembly of block copolymer discs and polymersomes with a cylinder line pattern on the surface that develops specific combinations of topological defects to satisfy the Euler characteristics for closed spheres as described by Gauss-Bonnet theorem. The dimension of the line pattern allows the direct visualization of defect emergence, evolution, and annihilation. On discs, cylinders either form end-caps that coincide with λ disclinations or they bend around τ disclinations in 180° turns (hairpin loops). On polymersomes, two λ defects connect into three-dimensional (3D) Archimedean spirals, while two τ defects form 3D Fermat spirals. Electron tomography reveals two complementary line patterns on the inside and outside of the polymersome membrane, where λ and τ disclinations always eclipse on opposing sides ("defect communication"). Attractive defects are able to annihilate with each other into +1 disclinations and stabilize anisotropic polymersomes with sharp tips through screening of high-energy curvature. This study fosters our understanding of the behavior of topological defects in self-assembled polymer materials and aids in the design of polymersomes with preprogrammed shapes governed by synthetic block length and topological rules.
拓扑结构和缺陷对于所有长度尺度上的有序结构都至关重要。尽管对溶液中的嵌段共聚物自组装进行了广泛研究，但关于拓扑缺陷及其对纳米结构形成的影响的知识仍然有限。在此，我们报道了具有表面圆柱线图案的嵌段共聚物圆盘和聚合物囊泡的自组装，该图案会形成特定的拓扑缺陷组合，以满足高斯 - 博内定理所描述的封闭球体的欧拉特征。线图案的尺寸使得缺陷的出现、演化和湮灭能够直接可视化。在圆盘上，圆柱要么形成与λ位错重合的端帽，要么以180°转弯（发夹环）围绕τ位错弯曲。在聚合物囊泡上，两个λ缺陷连接成三维（3D）阿基米德螺旋，而两个τ缺陷形成3D费马螺旋。电子断层扫描揭示了聚合物囊泡膜内部和外部的两种互补线图案，其中λ和τ位错总是在相对的两侧相互遮挡（“缺陷通信”）。有吸引力的缺陷能够相互湮灭形成 +1 位错，并通过屏蔽高能曲率来稳定具有尖锐尖端的各向异性聚合物囊泡。这项研究增进了我们对自组装聚合物材料中拓扑缺陷行为的理解，并有助于设计具有由合成嵌段长度和拓扑规则控制的预编程形状的聚合物囊泡。
