Orientational order parameters of a de Vries–type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction

A. Sanchez-Castillo, Mikhail A. Osipov, S. Jagiella, Z.H. Nguyen, M. Kaspar, V. Hamplova, J. Maclennan, F. Giesselmann

Research output: Contribution to journalArticle

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Abstract

The orientational order parameters 〈P2〉 and 〈P4〉 of the ferroelectric, de Vries–type liquid crystal 9HL have been determined in the SmA* and SmC* phases by means of polarized Raman spectroscopy, and in the SmA* phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a “sugar loaf” orientational distribution in the SmA* phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries–type behavior is considered.
LanguageEnglish
Article number061703
Number of pages18
JournalPhysical Review E
Volume85
Issue number6
DOIs
Publication statusPublished - 11 Jun 2012

Fingerprint

Raman Spectroscopy
Raman
X-ray Diffraction
Liquid Crystal
Order Parameter
x ray diffraction
Raman spectroscopy
liquid crystals
Raman Spectra
sugars
Sugars
x ray scattering
Density Functional
Discrepancy
Experiment
Fragment
Probe
Vibration
fragments
Scattering

Keywords

  • Ferroelectric liquid crystal
  • raman spectra
  • orientational order parameters
  • x-ray scattering

Cite this

Sanchez-Castillo, A. ; Osipov, Mikhail A. ; Jagiella, S. ; Nguyen, Z.H. ; Kaspar, M. ; Hamplova, V. ; Maclennan, J. ; Giesselmann, F. / Orientational order parameters of a de Vries–type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction. In: Physical Review E. 2012 ; Vol. 85, No. 6.
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Orientational order parameters of a de Vries–type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction. / Sanchez-Castillo, A.; Osipov, Mikhail A.; Jagiella, S.; Nguyen, Z.H.; Kaspar, M.; Hamplova, V.; Maclennan, J.; Giesselmann, F.

In: Physical Review E, Vol. 85, No. 6, 061703, 11.06.2012.

Research output: Contribution to journalArticle

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