由弯核分子组成的无极性双轴近晶-A相的实验证据
Experimental evidence of an Apolar Biaxial Smectic-A Phase Comprised of Bent-Core Molecules
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中文总结 AI 辅助
本研究通过多种实验手段证实了由不对称弯核分子构成的化合物中存在无极性双轴近晶-A相，该相具有特定相序列、双轴性质及显著电光响应。
中文摘要 AI 辅助
我们报道了对由不对称弯核分子构成的化合物所呈现的双轴近晶-A相的结构与物理研究。从各向同性相冷却时，该化合物呈现如下相序列：各向同性相（403.9 K）→双轴近晶-A相（359.8 K）→晶体。偏光光学显微镜、X射线衍射及极化反转电流测量明确证实了该近晶-A相的双轴性质，且无任何层极化。在该近晶-A相的整个温度范围内，测得的层间距接近分子长度。垂直取向样品中的纹影织构显示出±1/2和±1缺陷，表明该近晶-A相的双轴性质。对样品的介电谱研究揭示了德拜型弛豫过程，其弛豫时间随温度遵循阿伦尼乌斯方程。有趣的是，观察到的双轴近晶-A相对平面取向样品表现出显著的电光响应，且近晶层结构无任何重组。
英文摘要
We report structural and physical investigations on the biaxial smectic-A phase exhibited by a compound consisting of asymmetric bent-core molecules. Upon cooling from the isotropic phase, the compound exhibits the following phase sequence: Isotropic (403.9 K) $\rightarrow$ biaxial Smectic-A (359.8 K) $\rightarrow$ Crystal. The polarized optical microscopy, X-ray diffraction, and polarization reversal current measurements clearly establish the biaxial nature of the smectic-A phase without any layer polarization. The measured layer spacing in the entire temperature range of the smectic-A phase is close to the molecular length. The schlieren texture in a homeotropically aligned sample shows both $\pm \frac{1}{2}$ and $\pm 1$ defects which indicate the biaxial nature of this smectic-A phase. The dielectric spectroscopy studies on the samples revealed Debye-type relaxation processes with the relaxation time following the Arrhenius equation with temperature. Interestingly, the observed biaxial smectic-A phase exhibits a remarkable electro-optic response for a planar-aligned sample without any reorganization of the smectic layer structure.
