Sign Inversion of the Spontaneous Polarization in a "de Vries"‐Type Ferroelectric Liquid Crystal. Issue 7 (25th March 2014)

• Record Type: Journal Article
• Authors: Nonnenmacher, Dorothee; Lemieux, Robert P.; Osipov, Mikhail A.; Giesselmann, Frank
• Is Part Of: Chemphyschem. Volume 15:Issue 7(2014)
• Page Start: 1368
• Page End: 1375
• Publication Date: 2014-03-25
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201301154
• Languages: English
• ISSNs: 1439-4235

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>In contrast to common ferroelectric smectic C* liquid crystals, the siloxane‐terminated smectic mesogen <bold>E6</bold> 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 <bold>E6</bold> in the achiral SmC material <bold>C8Cl</bold>, 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 <bold>E6</bold> concentration. For the pure <bold>E6</bold> the inversion temperature meets the SmA*‐SmC* phase transition temperature. In a second binary mixture with <bold>E6</bold> and a conventional material <bold>C9</bold>–<bold>2PhP</bold> we found out, that the dependence of the inversion temperature on the concentration of <bold>E6</bold> 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.</p> </abstract>