Surface and interface designs in side-chain liquid crystalline polymer systems for photoalignment
Surface and interface designs in side-chain liquid crystalline polymer systems for photoalignment
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DOI：
10.1038/s41428-018-0100-4
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发表时间：
2018-07
期刊：
影响因子：
2.8
通讯作者：
Shusaku Nagano
中科院分区：
文献类型：
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作者：
Shusaku Nagano
在侧链液晶（SCLC）聚合物体系中，液晶（LC）介晶基团由于排除的体积效应（垂面排列）而优先垂直于基底平面取向。光响应偶氮苯（Az）介晶具有平行于分子长轴的跃迁矩。用于光反应的光照射通常垂直于膜表面施加。因此，垂面取向抑制Az SCLC聚合物系统中的有效光反应和光配向。本文综述了通过界面和表面分子设计在Az SCLC聚合物体系中诱导无规平面取向的新方法。通过表面引发的活性自由基聚合形成的高密度SCLC聚合物刷中的介晶采用无规平面取向。在具有无定形嵌段的SCLC嵌段共聚物的膜中，通过任一嵌段的表面偏析诱导随机平面取向。SCLC聚合物体系的无规平面取向是热稳定的，并且提供了具有分级LC分子架构的有效的平面内光配向和光开关，形成例如，微相分离（MPS）SCLC嵌段共聚物和层状聚合物LC系统。这些表面和界面的分子设计有望为液晶聚合物器件提供新的概念和可能性。
In side-chain liquid-crystal (SCLC) polymer systems, the liquid crystalline (LC) mesogenic groups preferentially orient normal to the substrate plane due to the excluded volume effect (homeotropic alignment). Photoresponsive azobenzene (Az) mesogens have a transition moment parallel to the molecular long axis. Light irradiation for photoreactions is generally applied perpendicular to the film surface. Therefore, a homeotropic orientation inhibits efficient photoreactions and photoalignments in Az SCLC polymer systems. This review focuses on new approaches to induce a random planar orientation in Az SCLC polymer systems by interface and surface molecular design. The mesogens in a high-density SCLC polymer brush formed by surface-initiated living radical polymerization adopt a random planar orientation. In the film of an SCLC block copolymer with an amorphous block, a random planar orientation is induced via surface segregation of either of the blocks. The random planar orientations of SCLC polymer systems are thermally stable and offer efficient in-plane photoalignment and photoswitching with hierarchical LC molecular architectures, forming, e.g., microphase-separated (MPS) SCLC block copolymers and layered polymer LC systems. These surface and interface molecular designs are expected to provide new concepts and possibilities for LC polymer devices.