The creation of long-lasting glassy columnar discotic liquid crystals using ‘dimeric’ discogens
作者:Neville Boden、Richard J. Bushby、Andrew N. Cammidge、Ahmed El-Mansoury、Philip S. Martin、Zhibao Lu
DOI:10.1039/a810045d
日期:——
âDimericâ discogens have been synthesised which have two triphenylene nuclei, each of which bears five β-OC
6
H
13
substituents, which are linked through the remaining β positions by a flexible O(CH
2
)
n
O polymethylene chain (n=3-16). Calculations show that the minimum chain length for bridging between columns in the Col
h
phase of these compounds is O(CH
2
)
7
O. It was found that only those dimers for which n>7 formed a Col
h
phase. This mesophase can be supercooled into a metastable glass which is relatively hard and in which the columnar order and orientation is retained. These glasses revert to the crystalline state within a few hours but we have shown that longer-lasting Col
h
glasses can be engineered through introducing an extra degree of disorder into the glass by making the âdimersâ subtly unsymmetrical. These âdimersâ either have differently substituted triphenylene rings at the two ends of the linking chain or an amide group within the chain itself. They give Col
h
aligned glasses which last for months at room temperature.
“二聚体”圆盘状分子已被合成,它们包含两个联苯并环己三烯核,每个核带有五个β-OC6H13取代基,通过剩余的β位点由柔性的O(CH2)nO聚甲撑链(n=3-16)连接。计算显示,这些化合物在Colh相中桥接列之间的最小链长为O(CH2)7O。研究发现,只有那些n>7的二聚体形成了Colh相。这种介相能过冷成相对坚硬且保持柱状有序和方向性的亚稳玻璃态。这些玻璃在几小时内会恢复到结晶态,但我们已证明,通过使“二聚体”微妙地不对称化,从而在玻璃中引入额外程度的无序,可以实现更持久Colh玻璃。这些“二聚体”在连接链的两端具有不同取代的联苯并环己三烯环,或在链本身内具有酰胺基团。它们生成的Colh有序玻璃在室温下可持续数月。