Room-temperature ferroelectric nematic liquid crystal showing a large and diverging density
Room-temperature ferroelectric nematic liquid crystal showing a large and diverging density
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室温铁电向列液晶显示出大且发散的密度
DOI：
10.1039/d3sm01282d
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发表时间：
2024
期刊：
影响因子：
3.4
通讯作者：
Parton-Barr C
中科院分区：
文献类型：
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作者：
Parton-Barr C
铁电液晶相（NF）是最近发现的一种物质相，其中传统液晶态的取向顺序被极性顺序增强。原子模拟表明，由于极性顺序的贡献，极性NF相将比传统的向列相更致密。使用振荡的U型管密度计，我们获得详细的温度依赖性的密度值的选择传统的液晶与先前的报告具有良好的协议。证明了我们的方法的有效性，然后我们记录密度作为温度的函数的M5，一种新型的室温铁电陶瓷材料。我们提出了第一个实验的NF材料的密度数据，以及以前没有被报道的密度数据为一个nanocomposite。我们发现，室温NF材料在所有研究温度下都显示出很大的密度（>1.3 g cm−3），特别是包括没有极性顺序的相。观察到相变时密度增加。中间体到铁电体的相变（NX-NF）的增加幅度比各向同性的相变（I-N）小一个数量级。然后，我们通过测量折射率（no和ne）来探测密度升高可能导致的潜在后果。将M5的navg与5CB和极性近晶液晶进行了比较。我们观察到系统的高极性性质如何抵消密度增加的影响。随着知识的实验密度，我们能够得到一个近似，产生的极性序参数，从偏振测量。目前的研究结果可能是典型的铁电材料，潜在的指导材料的发展，特别是相关的通知正在进行的研究这一类新兴的材料。
The ferroelectric nematic phase (NF) is a recently discovered phase of matter in which the orientational order of the conventional nematic liquid crystal state is augmented with polar order. Atomistic simulations suggest that the polar NF phase would be denser than conventional nematics owing to contributions from polar order. Using an oscillating U-tube densitometer, we obtain detailed temperature-dependent density values for a selection of conventional liquid crystals with excellent agreement with earlier reports. Having demonstrated the validity of our method, we then record density as a function of temperature for M5, a novel room-temperature ferroelectric nematic material. We present the first experimental density data for a NF material as well as density data for a nematic that has not previously been reported. We find that the room-temperature NF material shows a large (>1.3 g cm−3) density at all temperatures studied, notably including phases without polar order. An increase in density at phase transitions is observed. The magnitude of the increase for the intermediate-to-ferroelectric nematic (NX–NF) transition is an order of magnitude smaller than the isotropic–nematic (I–N) transition. We then probe potential consequences that may result from an elevated density through measurement of the refractive indices (no and ne). The navg of M5 is compared with 5CB and polar smectic liquid crystals. We observe how the highly polar nature of the system counteracts the effects of an increase in density. With knowledge of experimental density, we are able to derive an approximation that yields the polar order parameter, , from polarisation measurements. Present results may be typical of ferroelectric nematic materials, potentially guiding material development, and is especially relevant for informing ongoing studies into this emerging class of materials.