A novel series of styrene‐based liquid crystal monomers displaying either nematic or chiral nematic phases
A novel series of styrene‐based liquid crystal monomers displaying either nematic or chiral nematic phases
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一系列新型苯乙烯基液晶单体，具有向列相或手性向列相
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
A. Cook
中科院分区：
文献类型：
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作者：
N. McKeown;A. Cook
描述了一系列新的基于苯乙烯的液晶单体。这些单体通过DCC介导的4-[11-（4-乙烯基苯氧基）十一烷氧基]苯甲酸和一系列酚类之间的酯化反应制备，所述酚类是由于它们在液晶合成中的已证实的实用性而选择的。该系列的大多数成员显示热稳定（各向异性）的α相，虽然少数只给单致α相。通过引入（S）-2-甲基丁基侧链，可以获得表现出手性相的单体。可以预见的是，衍生自含有另外的环作为取代基的酚的单体（例如4-氰基-4 ′-羟基联苯）显示出相对高的转变温度。相比之下，衍生自简单的4-正烷基酚的单体具有在中等温度下可接近的α相。此外，衍生自这些单体的低共熔混合物具有仅略高于室温的熔点，这对于通过原位光聚合工艺制造坚固的膜是有利的。许多这些单体的标准自由基聚合提供侧链液晶聚合物SCLCP，其具有在宽温度范围内稳定的中间相。对于在介晶基团上含有末端正烷基链的SCLCP的同源系列，观察到意外但明显的奇偶效应。
A new series of liquid crystalline styrene‐based monomers is described. These monomers are prepared by the DCC‐mediated esterification reaction between 4‐[11‐(4‐vinylphenoxy)undecyloxy]benzoic acid and a range of phenols chosen due to their proven utility in the synthesis of liquid crystals. Most members of the series display thermally stable (enantiotropic) nematic phases, although a few give only monotropic nematic phases. By incorporating the (S)‐2‐methylbutyl side chain, monomers that exhibit the chiral nematic phase can be obtained. Predictably, monomers derived from phenols containing an additional ring as substituent (e.g. 4‐cyano‐4′‐hydroxybiphenyl) display relatively high transition temperatures. In contrast, monomers derived from simple 4‐n‐alkylphenols possess a nematic phase, which is accessible at moderate temperatures. In addition, a eutectic mixture derived from these monomers has a melting point only just above room temperature, which is an advantage for the fabrication of robust films via the in situ photopolymerization process. Standard free radical polymerization of a number of these monomers provides side chain liquid crystal polymers, SCLCPs, with mesophases that are stable over a wide temperature range. For a homologous series of SCLCPs containing a terminal n‐alkyl chain on the mesogenic group, an unexpected but distinct odd–even effect is observed.