Deuterium NMR spectra of the cholesteric and blue phases: A study of biaxiality
Deuterium NMR spectra of the cholesteric and blue phases: A study of biaxiality
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胆甾相和蓝相的氘核磁共振谱：双轴性研究
DOI：
10.1103/physreva.28.3012
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发表时间：
1983
影响因子：
2.9
通讯作者：
J. Doane
中科院分区：
文献类型：
--
作者：
Z. Yaniv;G. Chidichimo;J. Doane
从一组不同音高长度的胆甾材料的氘核磁共振光谱已经解释了分子的双轴顺序。我们发现，在这些材料中，只有当材料中存在蓝色相时，胆甾相的双轴性是还原温度的普遍函数（与节距长度无关）。相反，当胆甾相直接转变为各向同性相而不存在蓝色相时，还原温度图上的双轴性强烈依赖于节长。通过对同一分子不同氘化位点的研究，探讨了双轴性的机理。氘核磁共振谱也用于测量自扩散常数的基音依赖性。最后，对胆甾相双轴性的核磁共振测量技术进行了讨论和评价。用手性4-甲氧基苄基-4\ensuremath{'}-[(+)-2-甲基丁基]苯胺（MBMBA）以不同重量百分比选择性地对4-甲氧基苄基-4\ensuremath{'}-丁基苯胺（MBBA）进行氘化，得到不同节长样品。
Deuterium NMR spectra from a set of cholesteric materials differing in pitch length have been interpreted in terms of a biaxial ordering of the molecules. It is found that, in these materials, the biaxiality in the cholesteric phase is a universal function of the reduced temperature (independent of pitch length) only when there is a blue phase present in the material. In contrast, when the cholesteric phase transforms directly into the isotropic phase without the presence of a blue phase the biaxiality on a reduced-temperature plot is strongly pitch-length dependent. By the study of different deuterated sites of the same molecule, the mechanism for biaxiality is examined. Deuterium NMR spectra are also used to measure the pitch dependence of the self-diffusion constant. Finally, the NMR technique of measuring biaxiality in the cholesteric phase is discussed and a critique made. The materials used in the study were selectively deuterated 4-methoxybenzylidene-4\ensuremath{'}-butylaniline (MBBA) twisted by the addition of chiral 4-methoxybenzylidene-4\ensuremath{'}-[(+)-2-methylbutyl]aniline (MBMBA) in various weight percentages to obtain samples of different pitch lengths.