title: Polar Order and Symmetry Breaking at the Boundary between Bent-Core and Rodlike Molecular Forms: When 4-Cyanoresorcinol Meets the Carbosilane End Group.
abstract: Two isomeric achiral bent-core liquid crystals involving a 4-cyanoresorcinol core and containing a carbosilane unit as nanosegregating segment were synthesized and were shown to form ferroelectric liquid-crystalline phases. Inversion of the direction of one of the COO groups in these molecules leads to a distinct distribution of the electrostatic potential along the surface of the molecule and to a strong change of the molecular dipole moments. Thus, a distinct degree of segregation of the carbosilane units and consequent modification of the phase structure and coherence length of polar order result. For the compound with larger dipole moment (CN1) segregation of the carbosilane units is suppressed, and this compound forms paraelectric SmA and SmC phases; polar order is only achieved after transition to a new LC phase, namely, the ferroelectric leaning phase (SmCLs PS ) with the unique feature that tilt direction and polar direction coincide. The isomeric compound CN2 with a smaller dipole moment forms separate layers of the carbosilane groups and shows a randomized polar SmA phase (SmAPAR ) and ferroelectric polydomain SmCs PS phases with orthogonal combination of tilt and polar direction and much higher polarizations. Thus, surprisingly, the compound with the smaller molecular dipole moment shows increased polar order in the LC phases. Besides ferroelectricity, mirror-symmetry breaking with formation of a conglomerate of macroscopic chiral domains was observed in one of the SmC phases of CN1. These investigations contribute to the general understanding of the development of polar order and chirality in soft matter.
authors.affiliation: Institute of Chemistry, Organic Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120, Halle/Saale, Germany.|Department of Chemistry, Federal University of Santa Catarina, 88040-900, Florianópolis, Brazil.
authors.forename: Eduard
authors.initials: E
authors.lastname: Westphal
authors.affiliation: Department of Chemistry, Federal University of Santa Catarina, 88040-900, Florianópolis, Brazil.
authors.forename: Hugo
authors.initials: H
authors.lastname: Gallardo
authors.affiliation: Department of Chemistry, Federal University of Santa Catarina, 88040-900, Florianópolis, Brazil.
authors.forename: Giovanni Finoto
authors.initials: GF
authors.lastname: Caramori
authors.affiliation: Department of Nonlinear Phenomena, Institute for Experimental Physics, Otto von Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany.
authors.forename: Nerea
authors.initials: N
authors.lastname: Sebastián
authors.affiliation: Department of Nonlinear Phenomena, Institute for Experimental Physics, Otto von Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany.
authors.forename: Maria-Gabriela
authors.initials: MG
authors.lastname: Tamba
authors.affiliation: Department of Nonlinear Phenomena, Institute for Experimental Physics, Otto von Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany. alexey.eremin@ovgu.de.
authors.forename: Alexey
authors.initials: A
authors.lastname: Eremin
authors.affiliation: Department of Organic & Polymeric Materials, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo, 152-8552, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kawauchi
authors.affiliation: Institute of Chemistry, Organic Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120, Halle/Saale, Germany.
authors.forename: Marko
authors.initials: M
authors.lastname: Prehm
authors.affiliation: Institute of Chemistry, Organic Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120, Halle/Saale, Germany. carsten.tschierske@chemie.uni-halle.de.
authors.forename: Carsten
authors.identifier: 0000-0002-4163-3272
authors.initials: C
authors.lastname: Tschierske
keywords: bent-core mesogens; ferroelectrics; liquid crystals; mesophases; self-assembly