Liquid Crystalline Properties of Dimers Having o-, m- and p- Positional Molecular Structures

Bulletin of the Korean chemical society

Bong-Keun So¹  Hwan Myung Lee¹  Sung-Jo Kim¹  Jin-Young Lee¹  B. Ramaraj¹  Kyung-Hwan Kim¹   Kuk Ro Yoon¹  Dong-Hyun Kim¹  Joo-Hoon Park¹  Soo-Min Lee¹  Ok-Byung Choi¹  Eun-Hee Cha¹ 

关键词: Dimesogenic compounds;    Bent-shaped liquid crystals;    Differential scanning calorimetry;    Optical microscopy;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

With the objective to design and synthesis of Schiff`s base symmetrical liquid crystal dimmers and to study the effect of molecular structure variation (o-ortho, m-meta, p-para) and change in alkoxy terminal chain length on mesomorphic properties of liquid crystals, We have synthesized Schiff base dimers from dialdehyde derivative containing 2-hydroxy-1,3-dioxypropylene as short spacer with aniline derivatives having different lengths of terminal alkoxy chains (n = 5, 7, 9). The chemical structure of the final products was characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy and fourier transform infrared (FT-IR) spectroscopy. The mesomorphic properties and optical textures of the resultant dimers were characterized by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The existence of smectic A phase transition was confirmed by the observation of bâtonnets and fan shaped textures in optical microscopy when compound were heated from crystalline phase. All of the dimers of this series, with the exception of 2S5 -ortho, -meta, -para, were thermotropic liquid crystal. The compound 2S9 -meta was monotropic, while the rest were enantiotropic. It was found that the change in terminal alkoxy chain length has pronounced effect on the mesomorphic properties. The temperature range of smectic A phase window widens with increasing alkoxy chain length.

【 授权许可】

Unknown