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首页> 外文期刊>Liquid crystals today >Phase transitions from density and order parameter from polarisabilities in symmetric dimeric liquid crystals
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Phase transitions from density and order parameter from polarisabilities in symmetric dimeric liquid crystals

机译：对称二聚液晶的密度从相变到极化率的阶跃参数

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摘要

As a part of our systematic studies on liquid crystal dimers, we present in this article the nature of phase transitions across isotropic–nematic and nematic–smectic-A exhibited by DLCs, α,ω-bis-(4- n-alkylaniline benzylidene-4'-oxy) alkanes. Further, the orientational order parameter in the nematic phase of these DLCs are estimated from the molecular polarisabilities calculated using the experimental refractive indices and density results. The molecular polarisabilities αe and αo are obtained for the compounds using the above results for both Vuks and Neugebauer local field models applicable to nematic liquid crystal. α_e and α_o calculated in this way are used to obtain Δα. The polarisability anisotropy in the perfect order (absolute K) is calculated semiempirically using the δ-function model developed by Lippincott et al. and molecular vibration method. The values of polarisability anisotropy for both local electric field models differ significantly. No criterion is known to decide which value is correct. To avoid the determination of uncertain α and Δα values considering different local field models, a simple procedure developed by Kuczynski et al. was used for evaluation of S, based solely on birefringence δn = (ne-no) and this value of S is compared with those obtained from field models.
机译：作为我们对液晶二聚体的系统研究的一部分，我们在本文中介绍了DLC，α，ω-双-（4- n-烷基苯胺苄叉基- 4'-氧基）烷烃。此外，这些DLC的向列相中的取向顺序参数是根据使用实验折射率和密度结果计算出的分子极化率来估计的。使用适用于向列型液晶的Vuks和Neugebauer局部场模型的上述结果，可以得出这些化合物的分子极化率αe和αo。以这种方式计算的α_e和α_o用于获得Δα。使用Lippincott等人开发的δ函数模型，以半经验方式计算出理想阶数（绝对K）的极化率各向异性。和分子振动法。两种局部电场模型的极化率各向异性值均存在显着差异。尚无标准来确定哪个值正确。为了避免使用不同的局部场模型确定不确定的α和Δα值，Kuczynski等人开发了一种简单的程序。仅根据双折射δn=（ne-no），使用S的S值进行评估，并将S的这一值与从现场模型获得的S值进行比较。

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