AbstractIn 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.The liquid crystalline (LC) rod-like mesogens preferentially orient normal to the substrate plane due to the excluded volume effect (homeotropic alignment) in side-chain liquid-crystal (SCLC) polymers free-standing films. For in-plane alignment, a homeotropic orientation is unsuitable because the mesogens are in a direction opposite to the in-plane directions. This review focuses on new approaches to induce a random planar orientation in SCLC polymer systems by interface and surface molecular design utilizing a high-density polymer brush structure and surface segregation structures of block copolymers.

中文翻译：

---

用于光配向的侧链液晶聚合物系统的表面和界面设计

摘要在侧链液晶 (SCLC) 聚合物体系中，液晶 (LC) 介晶基团由于排除了体积效应（垂直排列）而优先垂直于基板平面取向。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，垂直取向抑制了 Az SCLC 聚合物系统中的有效光反应和光取向。本综述侧重于通过界面和表面分子设计在 Az SCLC 聚合物系统中诱导随机平面取向的新方法。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随机平面取向。在具有无定形嵌段的 SCLC 嵌段共聚物薄膜中，通过任一嵌段的表面偏析诱导无规平面取向。SCLC 聚合物系统的随机平面取向是热稳定的，并提供有效的面内光配向和具有分级 LC 分子结构的光开关，形成例如微相分离 (MPS) SCLC 嵌段共聚物和层状聚合物 LC 系统。这些表面和界面分子设计有望为 LC 聚合物器件提供新的概念和可能性。 由于侧链中排除的体积效应（垂直排列），液晶 (LC) 棒状介晶优先取向垂直于基板平面液晶 (SCLC) 聚合物自支撑薄膜。对于面内对齐，垂直取向是不合适的，因为介晶的方向与面内方向相反。本综述的重点是利用高密度聚合物刷结构和嵌段共聚物的表面分离结构，通过界面和表面分子设计在 SCLC 聚合物系统中诱导随机平面取向的新方法。