Liquid Crystalline Phase Induced by Molecular Rotator and Dipole Fluctuation
Liquid Crystalline Phase Induced by Molecular Rotator and Dipole Fluctuation
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分子旋转和偶极子涨落诱导液晶相
DOI：
10.1021/acs.cgd.5b00695
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发表时间：
2015
影响因子：
3.8
通讯作者：
T.
中科院分区：
文献类型：
--
作者：
Zhang;Q.-C.; Takeda;T.; Hoshino;N.; Noro;S.; Nakamura;T.; Akutagawa;T.
研究了新型棒状分子1和2的热性能、晶体结构、介电弛豫和旋转势能曲线，以阐明分子组合的动态分子行为和相变行为。1和2的分子结构不同，其中心芳香环为苯基（- c6h4 -） in1和吡啶基（- c5nh3 -） in2，由于分子2中无反转中心的永久偶极矩影响了相变行为。虽然晶体结构相同，但晶体2的熔点比晶体1低约43 K，并且在晶体2中可逆地观察到近晶a中间相。在差示扫描量热图上，由于热激活偶极子波动，晶体在加热过程中观察到广泛的吸热热异常，这与频率和温度相关的介电弛豫一致。通过密度泛函理论计算，- c6h4 -和- c5nh3 -环的旋转分别出现了双最小型和单最小型势能曲线。旋转对称性的差异影响了晶体的晶格能量和中间相的外观。
The thermal properties, crystal structures, dielectric relaxations, and rotational potential energy curves were examined for new rod-like molecules1and2bearing three aromatic rings connected by two -CONH- linkage groups to clarify the dynamic molecular behavior and phase transition behavior of the molecular assemblies. The molecular structures of1and2differed in that the central aromatic ring was phenyl (-C6H4-) in1and pyridyl (-C5NH3-) in2, which affected the phase transition behavior owing to the permanent dipole moment without the center of inversion in molecule2. Although the crystal structures of1and2were isostructural, the melting point of crystal2was approximately 43 K lower than that of crystal1, and a smectic A mesophase was reversibly observed in crystal2. A broad endothermic thermal anomaly of crystal2was observed in the heating process on the differential scanning calorimetry chart because of thermally activated dipole fluctuation, which was consistent with the frequency- and temperature-dependent dielectric relaxations. Double- and single-minimum-type potential energy curves were observed in the rotations of -C6H4- and -C5NH3- rings, respectively, from density functional theory calculations. The difference in rotational symmetry affected the crystal lattice energy and appearance of the mesophase.