Sign inversion of the spontaneous polarization in a “de Vries”-type ferroelectric liquid crystal

Dorothee Nonnenmacher, Robert Lemieux, Mikhail Osipov, Frank Giesselmann

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

In contrast to common ferroelectric smectic C* liquid crystals, the siloxane-terminated smectic mesogen E6 is characterized by an unusual temperature variation of the spontaneous polarization. The polarization starts to grow from nearly zero despite the first-order SmA*-SmC* transition, and increases faster than linearly over a large temperature interval while the tilt angle rapidly saturates. To study this behavior in more detail, binary mixtures of different concentrations of E6 in the achiral SmC material C8Cl, which has a similar chemical structure, were investigated. Surprisingly, all mixtures show a temperature dependent polarization sign inversion, which shifts towards the SmC*-SmA* transition with increasing E6 concentration. For the pure E6 the inversion temperature meets the SmA*-SmC* phase transition temperature. In a second binary mixture with E6 and a conventional material C9–2PhP we found out, that the dependence of the inversion temperature on the concentration of E6 changes qualitatively when the nanosegregation is partially destroyed. A molecular theory of the polarization sign inversion in smectics C* with strong polar intermolecular interactions is developed which enables one to explain the concentration dependence of the inversion temperature in both mixtures.
LanguageEnglish
Pages1368-1375
Number of pages8
JournalChemPhysChem
Volume15
Issue number7
Early online date25 Mar 2014
DOIs
Publication statusPublished - 19 May 2014

Fingerprint

Liquid Crystals
temperature inversions
Ferroelectric materials
liquid crystals
Polarization
inversions
polarization
binary mixtures
Binary mixtures
molecular theory
Temperature
siloxanes
Siloxanes
temperature
transition temperature
intervals
shift
Phase transitions
interactions

Keywords

  • chirality
  • liquid crystals
  • phase transitions
  • polarization
  • statistical mechanics

Cite this

Nonnenmacher, Dorothee ; Lemieux, Robert ; Osipov, Mikhail ; Giesselmann, Frank . / Sign inversion of the spontaneous polarization in a “de Vries”-type ferroelectric liquid crystal. In: ChemPhysChem. 2014 ; Vol. 15, No. 7. pp. 1368-1375.
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abstract = "In contrast to common ferroelectric smectic C* liquid crystals, the siloxane-terminated smectic mesogen E6 is characterized by an unusual temperature variation of the spontaneous polarization. The polarization starts to grow from nearly zero despite the first-order SmA*-SmC* transition, and increases faster than linearly over a large temperature interval while the tilt angle rapidly saturates. To study this behavior in more detail, binary mixtures of different concentrations of E6 in the achiral SmC material C8Cl, which has a similar chemical structure, were investigated. Surprisingly, all mixtures show a temperature dependent polarization sign inversion, which shifts towards the SmC*-SmA* transition with increasing E6 concentration. For the pure E6 the inversion temperature meets the SmA*-SmC* phase transition temperature. In a second binary mixture with E6 and a conventional material C9–2PhP we found out, that the dependence of the inversion temperature on the concentration of E6 changes qualitatively when the nanosegregation is partially destroyed. A molecular theory of the polarization sign inversion in smectics C* with strong polar intermolecular interactions is developed which enables one to explain the concentration dependence of the inversion temperature in both mixtures.",
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Sign inversion of the spontaneous polarization in a “de Vries”-type ferroelectric liquid crystal. / Nonnenmacher, Dorothee; Lemieux, Robert; Osipov, Mikhail; Giesselmann, Frank .

In: ChemPhysChem, Vol. 15, No. 7, 19.05.2014, p. 1368-1375.

Research output: Contribution to journalArticle

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N2 - In contrast to common ferroelectric smectic C* liquid crystals, the siloxane-terminated smectic mesogen E6 is characterized by an unusual temperature variation of the spontaneous polarization. The polarization starts to grow from nearly zero despite the first-order SmA*-SmC* transition, and increases faster than linearly over a large temperature interval while the tilt angle rapidly saturates. To study this behavior in more detail, binary mixtures of different concentrations of E6 in the achiral SmC material C8Cl, which has a similar chemical structure, were investigated. Surprisingly, all mixtures show a temperature dependent polarization sign inversion, which shifts towards the SmC*-SmA* transition with increasing E6 concentration. For the pure E6 the inversion temperature meets the SmA*-SmC* phase transition temperature. In a second binary mixture with E6 and a conventional material C9–2PhP we found out, that the dependence of the inversion temperature on the concentration of E6 changes qualitatively when the nanosegregation is partially destroyed. A molecular theory of the polarization sign inversion in smectics C* with strong polar intermolecular interactions is developed which enables one to explain the concentration dependence of the inversion temperature in both mixtures.

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