Effect of the linking unit on the twist-bend nematic phase in liquid crystal dimers: a comparative study of two homologous series of methylene- and ether-linked dimers
Effect of the linking unit on the twist-bend nematic phase in liquid crystal dimers: a comparative study of two homologous series of methylene- and ether-linked dimers
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DOI：
10.1080/02678292.2016.1240247
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发表时间：
2017-01-01
期刊：
影响因子：
2.2
通讯作者：
Goodby, John W.
中科院分区：
文献类型：
--
作者：
Archbold, Craig T.;Andrews, Jessica L.;Goodby, John W.
制备了两个系列的含苯甲酸苯酯基元的双介晶：一个系列含有一个七亚甲基间隔基，另一个系列含有一个五亚甲基间隔基和两个醚连接基团。制备这些材料以提供实验支持广泛持有的假设，即亚甲基连接的双介晶比它们的醚连接的对应物更可能表现出扭曲-弯曲双介晶相。几种亚甲基连接的材料表现出双相和N-TB中间相，而类似的醚连接的材料仅得到双相，尽管具有显著更高的清亮点。通过构建扭曲-弯曲材料CB 9 CB的二元相图，外推亚甲基和醚连接的双介晶的虚拟N-N-TB转变温度。与我们的预期相反，在大多数情况下，醚连接的双介晶的虚拟转变温度高于类似的亚甲基化合物，这与所报道的理论和假设背道而驰，即醚连接基团的引入应该起到使N-TB相不稳定的作用。[图形]。
Two series of bimesogens with phenyl benzoate mesogenic units were prepared: one series having a heptamethylene spacer and the other a pentamethylene spacer with two ether-linking groups. These materials were prepared to provide experimental backing to the widely held hypothesis that methylene-linked bimesogens are more likely to exhibit the twist-bend nematic mesophase than their ether-linked counterparts. Several of the methylene-linked materials exhibited nematic and N-TB mesophases, whereas the analogous ether-linked materials gave only nematic phases albeit with significantly higher clearing points. Virtual N-N-TB transition temperatures for both methylene-and ether-linked bimesogens were extrapolated by constructing binary phase diagrams with the well-studied twist-bend material CB9CB. Contrary to our expectations these virtual transition temperatures were in most cases higher for the ether-linked bimesogens than in the analogous methylene compounds, this runs counter to reported theories and hypotheses that the incorporation of ether-linking groups should serve to destabilise the N-TB phase.[GRAPHICS].