作者:Corrie T. Imrie、David Stewart、Catherine Rémy、David W. Christie、I. W. Hamley、R. Harding
DOI:10.1039/a901899i
日期:——
The first homologous series of liquid crystal tetramers in which four mesogenic groups are linked via three alkyl spacers has been synthesised and characterised. The length of the outer two spacers is varied from 3 to 12 methylene units while the central spacer is held at 8 methylene units. All the members of the series exhibit enantiotropic nematic behaviour except for the decyl and dodecyl homologues which exhibit exclusively smectic A behaviour. In addition, smectic A behavior is observed for the hexyl to dodecyl homologues. The transitional properties, namely the clearing temperatures and associated entropy changes, exhibit a dramatic odd–even effect as the length and parity of the outer spacers are varied. This behaviour is interpreted in terms of how the spacers control the average molecular shape. The ratio of the smectic periodicity to the estimated all trans molecular length for the nonyl homologue is just 0.27. Three differing local packing arrangements are suggested to account for this surprising result.
我们合成了第一个同源系列的液晶四聚体,其中四个介原基团通过三个烷基间隔物连接。外侧两个间隔物的长度从 3 个亚甲基单位到 12 个亚甲基单位不等,而中央间隔物则保持在 8 个亚甲基单位。除了癸基和十二烷基同系物只表现出共晶 A 行为外,该系列的所有成员都表现出对映向列行为。此外,从己基到十二烷基的同系物也具有共晶 A 行为。随着外间隔物长度和奇偶性的变化,过渡特性,即清除温度和相关熵变,表现出显著的奇偶效应。我们可以从间隔物如何控制平均分子形状的角度来解释这种行为。壬基同源物的构型周期性与估计的全反式分子长度之比仅为 0.27。为了解释这一令人惊讶的结果,我们提出了三种不同的局部堆积排列方式。
Thermotropic copolyazomethines and process for preparing them
申请人:ENIRICERCHE S.p.A.
公开号:EP0322943A2
公开(公告)日:1989-07-05
Thermotropic copolyazomethines having a mesophase temperature range lying within a desired range of values are obtained by copolymerizing terephthalic aldehyde with at least two different 1,n-bis(4-aminophenoxy)alkanes.
Such copolya omethines are particularly useful as reinforcing materials for the usual thermoplastic polymers, such as polycarbonate, polybutyleneterephthalate, polyethyleneterephthalate and polyamides.