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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Behavior of liquid crystals confined to mesoporous materials as studied by C-13 NMR spectroscopy of methyl iodide and methane as probe molecules
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Behavior of liquid crystals confined to mesoporous materials as studied by C-13 NMR spectroscopy of methyl iodide and methane as probe molecules

机译：甲基碘和甲烷作为探针分子的C-13 NMR光谱研究了局限在介孔材料中的液晶的行为

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The behavior of thermotropic nematic liquid crystals (LCs) Merck Phase 4 and ZLI 1115 confined to mesoporous controlled pore glass materials was investigated using C-13 nuclear magnetic resonance spectroscopy of probe molecules methyl iodide and methane. The average pore diameters of the materials varied from 81 to 375 angstrom, and the temperature series measurements were performed on solid, nematic, and isotropic phases of bulk LCs. Chemical shift, intensity, and line shape of the resonance signals in the spectra contain lots of information about the effect of confinement on the state of the LCs. The line shape of the C-13 resonances of the CH3I molecules in LCs confined into the pores was observed to be even more sensitive to the LC orientation distribution than, for example, that of H-2 spectra of deuterated LCs or Xe-129 spectra of dissolved xenon gas. The effect of the magnetic field on the orientation of LC molecules inside the pores was examined in four different magnetic fields varying from 4.70 to 11.74 T. The magnetic field was found to have significant effect on the orientation of LC molecules in the largest pores and close to the nematic-isotropic phase transition temperature. The theoretical model of shielding of noble gases dissolved in LCs based on pairwise additivity approximation was utilized in the analysis of CH4 spectra. For the first time, a first-order nematic-isotropic phase transition was detected to take place inside such restrictive hosts. In the larger pores a few degrees below the nematic-isotropic phase transition of bulk LC the C-13 quartet of CH3I changes as a powder pattern. Results are compared to those derived from Xe-129 NMR measurements of xenon gas in similar environments.
机译：使用探针分子甲基碘和甲烷的C-13核磁共振波谱研究了仅限于介孔受控孔玻璃材料的默克第四相和ZLI 1115的向列型向列液晶的行为。材料的平均孔径从81到375埃不等，并且对批量液相色谱的固相，向列相和各向同性相进行了温度序列测量。光谱中共振信号的化学位移，强度和线形包含许多有关限制对LC状态的影响的信息。观察到局限在孔中的LC中CH3I分子的C-13共振线形对LC方向分布甚至比氘化LC的H-2光谱或Xe-129光谱更敏感。溶解的氙气。在4.70至11.74 T之间的四个不同磁场中，研究了磁场对LC分子在孔内取向的影响。发现磁场对最大孔和密孔中LC分子的取向有显着影响向列各向同性的相变温度。在CH4光谱分析中，利用基于成对加性近似的LC溶解惰性气体屏蔽理论模型。首次在这种限制性宿主内部检测到一阶向列各向同性的相变。在本体LC的向列各向同性相变以下几度的较大孔中，CH3I的C-13四重态以粉末形式变化。将结果与在类似环境中从氙气的Xe-129 NMR测量得出的结果进行比较。

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