Kim Dae-Yoon, Park Minwook, Lee Sang-A, Kim Soeun, Hsu Chih-Hao, Kim Namil, Kuo Shiao-Wei, Yoon Tae-Ho, Jeong Kwang-Un
Department of Polymer-Nano Science and Technology & Polymer Materials Fusion Research Center, Chonbuk National University, Jeonju, Jeonbuk 561-756, Korea.
Soft Matter. 2015 Jan 7;11(1):58-68. doi: 10.1039/c4sm02239d.
Unconventional star-shaped liquid crystals (abbreviated as SiLCs) were successfully synthesized by chemically connecting four cyanobiphenyl anisotropic mesogens to the periphery of a super-hydrophobic and ultra-flexible cyclic tetramethyltetrasiloxane ring with flexible hexyl chains. Based on the combined experimental techniques of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), solid-state carbon-13 ((13)C) nuclear magnetic resonance (NMR) spectroscopy and one-dimensional (1D) wide-angle X-ray diffraction (WAXD), it was found that the SiLC molecule exhibited the monotropic phase transition from a LC phase to a crystalline phase. The crystalline phase was only detected during slow heating processes above its glass transition temperature, while a LC phase was formed both during cooling and during heating processes. The hierarchical superstructures were identified from the structure-sensitive 2D WAXD of the macroscopically oriented SiLC film and confirmed by selected area electron diffraction (SAED) of the SiLC single crystals. The molecular packing symmetry in the monoclinic unit cell was further investigated by computer simulations on the real and reciprocal spaces. Macroscopically oriented SiLC hierarchical superstructures on the different length scales may provide the targeted physical properties, which can allow us to apply SiLC molecules in the fields of electro-optical devices and nonlinear optics.
通过将四个氰基联苯各向异性介晶化学连接到具有柔性己基链的超疏水且超柔性的环状四甲基四硅氧烷环的外围，成功合成了非常规星形液晶（简称为SiLCs）。基于差示扫描量热法（DSC）、交叉极化光学显微镜（POM）、固态碳-13（(13)C）核磁共振（NMR）光谱和一维（1D）广角X射线衍射（WAXD）等综合实验技术，发现SiLC分子呈现出从液晶相到晶相的单向相变。仅在高于其玻璃化转变温度的缓慢加热过程中检测到晶相，而在冷却和加热过程中均形成液晶相。从宏观取向的SiLC薄膜的结构敏感二维WAXD中识别出分层超结构，并通过SiLC单晶的选区电子衍射（SAED）得到证实。通过在实空间和倒易空间上的计算机模拟，进一步研究了单斜晶胞中的分子堆积对称性。不同长度尺度上的宏观取向SiLC分层超结构可能提供目标物理性质，这使我们能够将SiLC分子应用于电光器件和非线性光学领域。
