Two mechanisms for the formation of ferronematic phase in DIO as studied by dielectric spectroscopy
Two mechanisms for the formation of ferronematic phase in DIO as studied by dielectric spectroscopy
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介电谱研究 DIO 中铁离子相形成的两种机制
DOI：
10.1016/j.molliq.2023.121570
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发表时间：
2023
影响因子：
6
通讯作者：
G. Mehl
中科院分区：
文献类型：
--
作者：
N. Yadav;Y. Panarin;J. Vij;Wanhe Jiang;G. Mehl
通过介电谱在 0.1 Hz–10 MHz 的频率范围内研究了介晶核心中具有 1,3-二恶烷单元的非手性铁电向列化合物，称为 2,3',4',5'-四氟-[1,1'-联苯]-4-基 2,6-二氟-4-(5-丙基-1,3-二恶烷-2-基)苯甲酸酯 (DIO)。温度。该化合物从各向同性相冷却后呈现出三个向列相，即普通的顺电向列N；中间向列相 NX 和铁电 NF 相。最小频率过程是由于离子的动力学造成的。中频弛豫过程 P1 类似于在其他铁素化合物中观察到的情况，这种模式是各向同性相中分子翻转运动到偶极子集体动力学的延续，偶极子集体动力学与向列相中的张开波动强烈耦合。除了这个过程之外，DIO 在 N 相和 NX 相中还显示了更高频率的附加集体弛豫过程 P2。这种模式起源于相反手性的极性/手性域，这些是由 N 相中非手性液晶元的自发对称性破缺引起的。两个集体过程 P1 和 P2 在从 N 冷却到 NX-NF 相变温度时表现出类似软模式的特征行为，并且显示出独立地有助于铁素 NF 相的形成。
A non-chiral ferroelectric nematic compound with a 1,3-dioxane unit in the mesogenic core called 2,3′,4′,5′-tetrafluoro-[1,1′-biphenyl]-4-yl 2,6-difluoro-4-(5-propyl-1,3-dioxan-2-yl) benzoate (DIO) was studied by dielectric spectroscopy in the frequency range 0.1 Hz–10 MHz over a wide range of temperatures. The compound exhibits three nematic phases on cooling from the isotropic phase, i.e., the ordinary paraelectric nematic N; the intermediate nematic NXand the ferroelectric NFphase. The least frequency process is due to the dynamics of ions. The middle frequency relaxation process P1is like as observed in other ferronematic compounds and this mode is a continuation of the molecular flip-flop motion in the isotropic phase to the collective dynamics of dipoles which are strongly coupled with the splay fluctuations in nematic phases. In addition to this process, DIO shows an additional collective relaxation process P2at higher frequencies both in the N and the NXphases. This mode originates from the polar/chiral domains of the opposite chirality, these arise from the spontaneous symmetry breaking of achiral mesogens in the N phase. Both collective processes, P1and P2, show soft mode-like characteristic behavior on cooling from the N to the NX-NFphase transition temperature and are shown to contribute independently to the formation of the ferronematic NFphase.
DOI：
10.1073/pnas.2002290117
发表时间：
2020-06-23
影响因子：
11.1
作者：
Chen, Xi;Korblova, Eva;Clark, Noel A.
通讯作者：
Clark, Noel A.