Electron beam irradiation-induced transformations in the electrical properties of 4'-octyl-4-cyanobiphenyl (8CB)

Changes in the dielectric and thermodynamical properties of electron beam-irradiated 4′-octyl-4-cyanobiphenyl (8CB) were studied. Irradiation-induced changes in the phase transition temperature, dielectric anisotropy, relaxation frequency and activation energy of an observed non-collective relaxatio...

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Bibliographic Details
Published in:Liquid crystals 2009-09, Vol.36 (9), p.1003-1014
Main Authors: Verma, Rohit, Dhar, R., Agrawal, V. K., Rath, M. C., Sarkar, S. K., Wadhawan, V. K., Dabrowski, R.
Format: Article
Language:English
Subjects:
Anisotropy
dielectric parameters
Dielectric properties
Electric properties
electron beam irradiation
Electrons
Fourier transform infrared spectroscopy
Mass spectrometry
Phase transitions
relaxation frequency
Spectrum analysis
UV-visible
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Summary:Changes in the dielectric and thermodynamical properties of electron beam-irradiated 4′-octyl-4-cyanobiphenyl (8CB) were studied. Irradiation-induced changes in the phase transition temperature, dielectric anisotropy, relaxation frequency and activation energy of an observed non-collective relaxation mode corresponding to molecular rotation about the short axis were determined in both nematic and smectic A d phases. In the nematic phase, dielectric anisotropy increased for a small dose but decreased for a relatively high dose, whereas the relaxation frequency increased due to the irradiation. The pure and irradiated samples were characterised by UV-visible spectroscopy, Fourier transform infrared spectroscopy, gas chromatography, gas chromatography coupled with mass spectroscopy and pulse radiolysis. The observed changes in the dielectric parameters are related to the detachment of the CN group from some of the 8CB molecules due to the electron beam irradiation.
ISSN:0267-8292
1366-5855
DOI:10.1080/02678290903220972