Ideal mixing of paraelectric and ferroelectric nematic phases in liquid crystals of distinct molecular species
Ideal mixing of paraelectric and ferroelectric nematic phases in liquid crystals of distinct molecular species
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DOI：
10.1080/02678292.2022.2058101
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发表时间：
2022-05-02
期刊：
影响因子：
2.2
通讯作者：
Clark, Noel A.
中科院分区：
文献类型：
--
作者：
Chen, Xi;Zhu, Zhecong;Clark, Noel A.
有机介晶RM 734和DIO是具有不同分子结构的独立分子家族的成员。这些家族是第一个已知的表现出铁电液晶相。在这里，我们提出了一个实验研究的相图和电光的二元混合物RM 734和DIO。我们观察到顺电体和铁电体在这两种材料中，其中每一个都表现出完整的可兼容性的相图，表明顺电体和铁电体是在RM 734和DIO相同的阶段。值得注意的是，这些分子相对于顺电-铁电双相行为和混合物的铁电极化密度（过渡的主要序参数）形成理想的混合物。理想的混合还表现在取向粘度和低温下玻璃态动力学的开始。这种行为部分归因于它们的整体分子形状和净纵向偶极矩的相似性，以及头到尾分子缔合的共同趋势。相比之下，分子结构的显著差异导致在晶相中的溶解度差，从而增强了混合物中铁电介电相在低温下的稳定性，并且能够实现室温电光效应。
The organic mesogens RM734 and DIO are members of separate molecular families featuring distinct molecular structures. These families are the first ones known to exhibit a ferroelectric nematic liquid crystal phase. Here, we present an experimental investigation of the phase diagram and electro-optics of binary mixtures of RM734 and DIO. We observe paraelectric nematic and ferroelectric nematic phases in both materials, each of which exhibits complete miscibility across the phase diagram, showing that the paraelectric and ferroelectric are the same phases in RM734 and DIO. Remarkably, these molecules form ideal mixtures with respect to both the paraelectric-ferroelectric nematic phase behaviour and the ferroelectric polarisation density of the mixtures, the principal order parameter of the transition. Ideal mixing is also manifested in the orientational viscosity, and the onset of glassy dynamics at low temperature. This behaviour is attributable in part to the similarity of their overall molecular shape and net longitudinal dipole moment, and to a common tendency for head-to-tail molecular association. In contrast, the significant difference in molecular structures leads to poor solubility in the crystal phases, enhancing the stability of the ferroelectric nematic phase at low temperature in the mixtures and enabling room-temperature electro-optic effects.