Formation of homochiral helical nanostructures in diblock copolymers under the confinement of nanopores
Formation of homochiral helical nanostructures in diblock copolymers under the confinement of nanopores
复制标题
纳米孔限制下二嵌段共聚物中纯手性螺旋纳米结构的形成
DOI：
10.1039/c9cp00227h
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发表时间：
2019
影响因子：
3.3
通讯作者：
Li Weihua
中科院分区：
文献类型：
--
作者：
Yang Tao;Xue Haiyan;Cao Ruifang;Li Weihua
控制非手性体系中形成的螺旋结构的同色性是人们非常感兴趣的问题，因为它有助于理解生命中同性的起源。在这项工作中，我们在纳米孔的内表面引入了螺旋排列的补丁，以引导圆柱形AB两嵌段共聚物熔体自组装成同手性的单螺旋。用自洽场理论(SCFT)计算了不同作用力的单螺旋结构的自由能。此外，我们还利用从无序态开始的SCFT解的迭代过程模拟了自组装过程，并计算了不同螺旋结构的形成几率。我们发现，具有良好自由能的同手性螺旋的形成几率迅速增加，从而得出这样的结论：每条链上微小的差异0.5-1.0×10−4kBT就足以通过抑制其对应的较高自由能而获得同手性螺旋。然而，对于更强的手性导向场，更有可能形成其他具有不利利手性的同手性螺旋结构，从而更容易形成越来越高的自由能。自组装过程中的形态快照表明，这些亚稳态螺旋结构的形成是由它们的动力学路径诱导的，而这些动力学路径被贴片图案的强手征场改变为有利的。因此，我们的工作表明热力学和动力学对于控制螺旋结构的手性都是重要的。
The control of the homochirality of helical structures formed in achiral systems is of great interest as it is helpful for understanding the origin of homochirality in life. In this work, we introduce a spiral arrangement of patches into the inner surface of a nanopore to guide the self-assembly of a cylinder-forming AB diblock copolymer melt into a homochiral single helix. We calculate the free energy of the single-helical structures with different handedness using self-consistent field theory (SCFT). Moreover, we simulate the self-assembly process using an iterative process of SCFT solution starting from a disordered state, and count the formation probability of different helical structures. We find that the formation probability of the homochiral helix with favorable free energy increases rapidly, leading to the conclusion that a minuscule difference of 0.5–1.0 × 10−4kBT per chain is enough to obtain the homochiral helix by suppressing its counterpart of a higher free energy. However, for a stronger chiral guiding field, other homochiral helical structures with unfavorable handedness and thus increasingly higher free energy become more likely to be formed. Morphological snapshots during the self-assembly process reveal that the formation of these metastable helical structures is induced by their kinetic pathways, which are altered to be favorable by the strong chiral field of the patch pattern. Therefore, our work suggests that both thermodynamics and kinetics are important for controlling the chirality of helical structures.