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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Phase Characterization and Study of Molecular Order of a Three-Ring Mesogen by ~(13)C NMR in Smectic C and Nematic Phases
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Phase Characterization and Study of Molecular Order of a Three-Ring Mesogen by ~(13)C NMR in Smectic C and Nematic Phases

机译：在近碳相和向列相中〜（13）C NMR的三环液晶元的相表征和分子序研究

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摘要

Molecules exhibiting a thermotropic liquid-crystalline property have acquired significant importance due to their sensitivity to external stimuli such as temperature, mechanical forces, and electric and magnetic fields. As a result, several novel mesogens have been synthesized by the introduction of various functional groups in the vicinity of the aromatic core as well as in the side chains and their properties have been studied. In the present study, we report three-ring mesogens with hydroxyl groups at one terminal. These mesogens were synthesized by a multistep route, and structural characterization was accomplished by spectral techniques. The mesophase properties were studied by hot-stage optical polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. An enantiotropic nematic phase was noticed for lower homologues, while an additional smectic C phase was found for higher homologues. Solid-state high-resolution natural abundance ~(13)C NMR studies of a typical mesogen in the solid phase and in the mesophases have been carried out. The ~(13)C NMR spectrum of the mesogen in the smectic C and nematic phases indicated spontaneous alignment of the molecule in the magnetic field. By utilizing the two-dimensional separated local field (SLF) NMR experiment known as SAMPI4,~(13)C—~1H dipolar couplings have been obtained, which were utilized to determine the orientational order parameters of the mesogen.
机译：由于其对诸如温度，机械力以及电场和磁场之类的外部刺激的敏感性，表现出热致液晶性质的分子已经变得非常重要。结果，通过在芳族核附近以及在侧链中引入各种官能团，已经合成了几种新颖的介晶，并且已经研究了它们的性质。在本研究中，我们报告了在一个末端带有羟基的三环液晶元。这些介晶通过多步路线合成，并通过光谱技术完成结构表征。通过热阶段光学偏振显微镜，差示扫描量热法和小角X射线散射研究了中间相性质。较低的同系物注意到对映向列相，而较高的同系物则发现了另外的近晶C相。已经进行了固态和中间相中典型介晶的固态高分辨率自然丰度〜（13）C NMR研究。在近晶C相和向列相中液晶元的〜（13）C NMR谱表明该分子在磁场中自发排列。通过利用称为SAMPI4的二维分离局部场（SLF）NMR实验，获得了〜（13）C ~~ 1H双极偶合，用于确定液晶元的取向顺序参数。

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