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首页> 外文期刊>Zeitschrift fur Naturforschung. A, A journal of physical sciences >Dielectric Relaxation Studies of 4-n-Alkyloxy-4'-Cyanobiphenyls (nOCB, n = 5/8)
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Dielectric Relaxation Studies of 4-n-Alkyloxy-4'-Cyanobiphenyls (nOCB, n = 5/8)

机译：4-n-烷氧基-4'-氰基联苯（nOCB，n = 5/8）的介电弛豫研究

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摘要

The results of dielectric relaxation studies of series of four n-alkyloxy cyanobiphenyl (nOCB) compounds with n ranging from 5 to 8 are presented. The complex dielectric permittivity, ε~*(ω) = ε′(ω)—i ε″(ω), was measured in the frequency range 1 kHz-3 GHz, with the use of an impedance analyzer and a time domain spectroscopy (TDS) set-up. The relaxation times: longitudinal τ_‖ in the nematic and smectic A phase (8 OCB), transverse τ_⊥ in the nematic phase, and τ_(is) in the isotropic phase, were obtained as functions of the temperature. This allowed the calculation of activation barriers for different molecular relaxation processes occurring in particular phases. Moreover, the retardation factors g_‖ and g_⊥ and the nematic potential q according to two theoretical models were calculated. The analysis of q(T) and its relation to the order parameter S is done taking into account the results of NMR studies of the compounds under consideration. Finally, the dependencies of the obtained quantities on the number of carbon atoms in the alkyloxy chains are analyzed.
机译：给出了一系列n范围为5至8的四种n-烷氧基氰基联苯（nOCB）化合物的介电弛豫研究结果。复介电常数ε〜*（ω）=ε'（ω）-iε''（ω）在1 kHz-3 GHz频率范围内使用阻抗分析仪和时域光谱仪（ TDS）设置。弛豫时间：作为向列相和近晶A相的纵向τ_‖（8 OCB），向列相的横向τ_⊥和各向同性相的τ_（is）作为温度的函数。这样就可以计算出在特定阶段发生的不同分子弛豫过程的激活势垒。此外，根据两个理论模型计算了延迟因子g_′和g_⊥以及向列电势q。考虑到所考虑化合物的NMR研究结果，对q（T）及其与阶数参数S的关系进行了分析。最后，分析了所得量对烷氧基链中碳原子数的依赖性。

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