Unconventional ferroelectric behavior in nanosegregating liquid crystals with de Vries-like behavior.
Unconventional ferroelectric behavior in nanosegregating liquid crystals with de Vries-like behavior.
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纳米偏析液晶中具有类似德弗里斯行为的非常规铁电行为。
DOI：
10.1103/physreve.82.031703
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Nonnenmacher D
中科院分区：
文献类型：
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作者：
Nonnenmacher D
合成了两种具有手性2，3-环氧辛氧基侧链的纳米隔离型聚硅氧烷封端液晶基元（E6，E11）。这些化合物形成手性相，并显示出非典型的自发极化行为，其随温度降低以凸的方式增加，而倾斜角饱和。我们将这些结果与两个类似的具有手性-2，3-二氟辛氧基侧链的介晶（F6，F11）的结果进行了比较，这两个介晶都显示出典型的凹曲率随温度的降低。对自发极化的温度依赖性给出了理论解释。该材料还表现出一阶相变，因此，非常高的值的倾斜角。所有物质都显示出在50%范围内的增加的de弗里斯特性，其显著高于非硅氧烷类似物的20%。此外，对于后者的材料，二阶相变是常见的，而硅氧烷材料表现出一阶相变。这些结果清楚地表明，纳米偏析的实现是一个强大的工具，诱导德弗里斯行为，并促进一阶相变。
Two nanosegregating siloxane-terminated mesogens with chiral-2,3-epoxyoctyloxy side chains (E6,E11)have been synthesized. These compounds form chiralandphases and show an untypical behavior of the spontaneous polarization which increases with decreasing temperature in a convex manner while the tilt angle saturates. We compare these results with results obtained for two similar mesogens with chiral-2,3-difluorooctyloxy side chains (F6,F11), which both show a typical concave curvature with decreasing temperature. A theoretical explanation is given for the unexpected temperature dependency of the spontaneous polarization. The materials also exhibited first-orderphase transitions and hence, very high values of the tilt angle. All substances show increased de Vries character in the range of 50%, which is substantially higher than 20% for the nonsiloxane analogs. Furthermore, for the latter materials, second-order phase transitions are common, while the siloxane materials exhibit first-orderphase transitions. These results clearly suggest that the achievement of nanosegregation is a powerful tool to induce de Vries behavior and to promote first-orderphase transitions.