Orientational Ordering of a Dimer Liquid Crystal by High-Resolution Solid-State 13C NMR Spectroscopy
Orientational Ordering of a Dimer Liquid Crystal by High-Resolution Solid-State 13C NMR Spectroscopy
复制标题
通过高分辨率固态 13C NMR 光谱对二聚体液晶进行定向排序
DOI：
10.1295/polymj.29.598
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发表时间：
1997
期刊：
影响因子：
2.8
通讯作者：
S. Kuroki
中科院分区：
文献类型：
--
作者：
Renato Norio Shimizu;H. Kurosu;I. Ando;A. Abe;Hidemine Furuya;S. Kuroki
用变温高分辨固体~（13）C NMR研究了α，ω-双[（4，4 ′-氰基联苯基）氧基]癸烷（CBA-10）二聚体液晶的有序化.由于分子的单轴取向，在从各向同性相到均质相的过程中观察到13 C化学位移的大的过渡变化。本文用Herzbert-Berger方法测定了CBA-10的~（13）C化学位移张量的主值。假设分子轴平行于连接两个介晶核中心的直线，并计算了分子轴（Szz）、介晶轴（Szzring）和Cγ−Cε轴上的序参数沿着。利用得到的各向同性~（13）C化学位移和~（13）C化学位移张量的主值，并在旋转异构态（RIS）方法的框架下考虑了柔性间隔基的构象行为。从向列相-各向同性转变点附近开始，随着温度的降低17.5°C，分子的有序参数Szz从0.79增加到0.89。随着温度的降低，Szzring从0.74增加到0.80，而SzzCγ-Cε和间隔子的构象在相同的温度范围内基本不变。
The ordering of a dimer liquid crystal, α,ω-bis[(4,4′-cyanobiphenylyl)oxy]decane (CBA-10), was studied by variable-temperature high-resolution solid-state 13C NMR. A large transitional change of the 13C chemical shift was observed on going from the isotropic to the nematic phase due to uniaxial alignment of the molecule. The principal values of the 13C chemical shift tensor have been determined by the Herzfeld-Berger method for CBA-10 itself. The molecular axis is assumed to lie parallel to the line connecting the centers of both mesogenic cores, and the evaluation of the order parameters along the molecular axis, (Szz), mesogene axis (Szzring) and Cγ−Cε axis (SzzCγ-Cε) was attempted here, using the obtained isotropic 13C chemical shift and principal values of the 13C chemical shift tensor, and taking into account the conformational behavior of the flexible spacer in the frame of rotational isomeric state (RIS) approach. The order parameter of the molecule Szz increased from 0.79 to 0.89 with decrease of 17.5°C in temperature from nearby the nematic-isotropic transition point. Szzring increased from 0.74 to 0.80 with decrease of temperature whereas SzzCγ-Cε and the conformation of the spacer was essentially unaltered in the same temperature range.