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Effects of Molecular Length on Nematic Mixtures

 

作者: J.David Margerum,   JohnE. Jensen,   AnnaM. Lackner,  

 

期刊: Molecular Crystals and Liquid Crystals  (Taylor Available online 1981)
卷期: Volume 68, issue 1  

页码: 137-156

 

ISSN:0026-8941

 

年代: 1981

 

DOI:10.1080/00268948108073560

 

出版商: Taylor & Francis Group

 

数据来源: Taylor

 

摘要:

The properties of nematic mixtures of 4-alkoxyphenyl 4-alkylbenzoates are studied as a function of their average molecular length (L). The L's of the mixtures vary between 20.46 and 27.14 Å, but they all have clearpoints in the 51 to 58° C range. The flow viscosity increases linearly with L. The dielectric constant, refractive index, birefringence, and density decrease linearly with L, and the dielectric anisotropy becomes more negative. With tetrabutylammonium tetraphenylboride added as a salt dopant, the conductivity anisotropy (σ∥/στ) decreases with increasing L, and the dynamic-scattering (DS) threshold voltage increases correspondingly. The effect of L on the DS decay time (τD) is highly dependent on the surface alignment. In surface ⊥ cells, τDincreases strongly with L, while in surface ∥ cells, τDdecreases slightly with increasing L. The temperature dependence of σ∥/στindicates that the longer L mixtures, with about ten or more total alkyl carbons from both end groups, have cybotactic nematic characteristics.

 

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