DIO向列相和近晶ZA相的fredericksz跃迁。

IF 2.9 3区 化学 Q3 CHEMISTRY, PHYSICAL
Soft Matter Pub Date : 2025-06-27 DOI:10.1039/d5sm00238a
J T Gleeson, S N Sprunt, A Jákli, P Guragain, R J Twieg
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引用次数: 0

摘要

非凡的材料DIO表现出令人着迷的行为。作为最早表现出铁电向列相的材料之一,它得到了广泛的研究。然而,在较高的温度下,它表现出所谓的近晶ZA:被确定为取向有序的反铁电相,具有垂直于光轴方向的密度调制。在更高的温度下,这转变为明显的正常向列相。我们研究了材料DIO向列相和SmZA相的斜弯fredericksz跃迁。磁场和电场的跃迁都被利用。我们通过测量有效双折射和电容以及偏光显微镜观察了这种转变。在向列态和SmZA态中,场诱导的跃迁(在许多方面)与经典的fredericksz跃迁相似。这些可以确定几个基本的材料参数,也揭示了SmZA相的有趣方面,包括弹性常数和介电各向异性的惊人行为。与fredericksz相变的Frank弹性理论的详细比较表明,N相的行为与预期基本一致,但SmZA相的转变有很大不同。这方面的两个具体例子是弗里德里克斯扭曲态中条纹的出现,以及光学双轴性的存在。前者可能与周期性的fredericksz转变有关,因为它与横向弹性常数的大幅增加相吻合。后者已经被预测为SmZA期,但以前没有观察到。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Freedericksz transitions in the nematic and smectic ZA phases of DIO.

The remarkable material DIO presents fascinating behaviors. It has been extensively studied as one of the first materials exhibiting a ferroelectric nematic phase. However, at higher temperatures it exhibits what has been termed the smectic ZA: identified as an orientationally ordered, antiferroelectric phase with a density modulation in direction perpendicular to the optic axis. At even higher temperatures, this transitions to an apparently normal nematic phase. We have studied the splay-bend Freedericksz transition in the nematic and SmZA phases of the material DIO. Both the magnetic and electric field transitions were utilized. We observed the transitions by measuring effective birefringence and capacitance as well as with polarizing light microscopy. In both the nematic and the SmZA states the field induced transitions resemble (in numerous aspects) the classical Freedericksz transition. These enable determinations of several fundamental material parameters and also reveal intriguing aspects of the SmZA phase, including the surprising behavior of the elastic constants and the dielectric anisotropy. Detailed comparison with Frank elastic theory of the Freedericksz transition shows that the N phase behaves largely as expected, but the transition in the SmZA phase differs significantly. Two specific examples of this are the onset of striations in the Freedericksz distorted state, and the presence of optical biaxiality. The former may be related to the periodic Freedericksz transition as it coincides with a large increase in the splay elastic constant. The latter has been predicted for the SmZA phase, but not previously observed.

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来源期刊
Soft Matter
Soft Matter 工程技术-材料科学:综合
CiteScore
6.00
自引率
5.90%
发文量
891
审稿时长
1.9 months
期刊介绍: Soft Matter is an international journal published by the Royal Society of Chemistry using Engineering-Materials Science: A Synthesis as its research focus. It publishes original research articles, review articles, and synthesis articles related to this field, reporting the latest discoveries in the relevant theoretical, practical, and applied disciplines in a timely manner, and aims to promote the rapid exchange of scientific information in this subject area. The journal is an open access journal. The journal is an open access journal and has not been placed on the alert list in the last three years.
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