Comparison of short range interactions in nematic liquid crystals A2H-NMR study of 5CB-d19as a solute
作者:
T. Chandrakumar,
DanS. Zimmerman,
G.S. Bates,
E.Elliott Burnell,
期刊:
Liquid Crystals
(Taylor Available online 1994)
卷期:
Volume 17,
issue 4
页码: 457-485
ISSN:0267-8292
年代: 1994
DOI:10.1080/02678299408036733
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Previous studies using dideuterium as a solute have demonstrated the importance for orientation of the interaction between the solute molecular quadrupole moment and the average electric field gradient present in liquid crystals. With the aim of learning about additional orientational mechanisms, we have studied the temperature dependence of the2H-NMR spectra of the liquid crystal 5CB-d19as the solute in three liquid crystal mixtures: 55 wt % 1132/EBBA, 56·5 wt % 1132/EBBA and 70 wt % 5CB/EBBA. In these mixtures, the contribution from the environment to the average electric field gradient at the2H nucleus of dideuterium is zero. The spectra of 5CB-d19in the mixtures 55 wt % 1132/EBBA and 56·5 wt % 1132/EBBA are equivalent, but are different from those in 70 wt % 5CB/EBBA. The spectra of 5CB in 55 wt % 1132/EBBA and 70 wt % 5CB/EBBA are analysed using two different models for the short range potential, and param eters of the models are used to compare the potentials in the different mixtures. For a given spectral splitting of the chain C1deuteron, the reduced short range potential is the same in all three mixtures studied. The spectral differences observed are a consequence of different nematic-isotropic phase transition temperatures combined with the effect oftrans/gauche-isomerization in the hydrocarbon chain.
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