Molecular alignment and thermal stability of liquid-crystalline phases in binary mixtures of electron donor and acceptor
Molecular alignment and thermal stability of liquid-crystalline phases in binary mixtures of electron donor and acceptor
复制标题
DOI：
10.1016/j.molstruc.2004.11.007
复制
发表时间：
2005-02-14
影响因子：
3.8
通讯作者：
Abe, J
中科院分区：
文献类型：
--
作者：
Han, SH;Yoshida, H;Abe, J
用DSC研究了由两种不同的席夫碱液晶材料D（含给电子-N（CH 3）（2）单元）和A（含吸电子-NO2单元）组成的混合物DA的分子取向和热稳定性。POM、XRD和FT-IR测量。混合物DA的中间相比单独的化合物D和A的中间相更稳定并且具有更宽的温度范围。混合物DA 55（D：A = 50：50摩尔%）在冷却时表现出最稳定的液晶相，在所检测的混合物DA中提供最高的T-SI（119 ℃）、最宽的近晶相温度范围（46.4 ℃）和最高的Δ S（SI）值（26.1 J K-1 mol（-1））。通过XRD测试和FT-IR光谱的温度依赖性分析，推测DA 55混合物的分子堆积在近晶A相中形成双层结构，其中化合物D和A的头基部分重叠。近晶相的诱导和混合物DA的热稳定性的增强可能是由于电子给体和受体介晶之间的分子间相互作用引起的。(C)2005 Elsevier B. V.保留所有权利。
The molecular alignment and thermal stability of the mixtures DA composed of two different kinds of Schiff base liquid-crystalline materials, D with an electron-donating -N(CH3)(2) unit and A with an electron-withdrawing-NO2 unit, were investigated by using DSC. POM, XRD, and FT-IR measurements. The mesophases of the mixtures DA were more stable and had wider temperature ranges than those of the individual compounds D and A. The mixture DA55 (D:A = 50:50 mol%) on cooling exhibited the most stable liquid-crystalline phases affording the highest T-SI (119 degreesC), the widest temperature range of the smectic phase (46.4 degreesC) and the highest values of DeltaS(SI) (26.1 J K-1 mol(-1)) among the mixtures DA examined. Based on the analysis of the XRD measurements and the temperature dependence on the FT-IR spectra, the molecular packing of the mixture DA55 was proposed to form a bilayer structure in the smectic A phase, in which the heading group of the compounds D and A overlapped partially. The induction of the smectic phase and the enhanced thermal stability for the mixtures DA would be caused by the intermolecular interaction between the electron donor and acceptor mesogens. (C) 2005 Elsevier B.V. All rights reserved.