Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
RIKEN Center for Emergent Matter Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
Nat Commun. 2016 Nov 29;7:13640. doi: 10.1038/ncomms13640.
How to orient polymers homeotropically in thin films has been a long-standing issue in polymer science because polymers intrinsically prefer to lie down. Here we provide a design principle for polymers that are processable into a 2D homeotropic order. The key to this achievement was a recognition that cylindrical polymers can be designed to possess oppositely directed local dipoles in their cross-section, which possibly force polymers to tightly connect bilaterally, affording a 2D rectangular assembly. With a physical assistance of the surface grooves on Teflon sheets that sandwich polymer samples, homeotropic ordering is likely nucleated and gradually propagates upon hot-pressing towards the interior of the film. Consequently, the 2D rectangular lattice is constructed such that its b axis (side chains) aligns along the surface grooves, while its c axis (polymer backbone) aligns homeotropically on a Teflon sheet. This finding paves the way to molecularly engineered 2D polymers with anomalous functions.
如何使聚合物在薄膜中各向异性排列一直是聚合物科学中的一个长期存在的问题，因为聚合物本质上更倾向于躺下。在这里，我们提供了一种可将聚合物加工成二维各向异性排列的设计原则。这一成就的关键是认识到圆柱状聚合物可以被设计成在其横截面上具有相反方向的局部偶极子，这可能迫使聚合物紧密地双侧连接，形成二维矩形组装。在聚四氟乙烯片表面凹槽的物理辅助下，各向异性排列可能在热压过程中从薄膜内部开始形成并逐渐扩展。因此，二维矩形晶格的构建方式使得其 b 轴（侧链）沿表面凹槽排列，而其 c 轴（聚合物主链）在聚四氟乙烯片上各向异性排列。这一发现为具有异常功能的分子工程二维聚合物铺平了道路。
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