& Liquid Crystals Polar Order and Symmetry Breaking at the Boundary between Bent-Core and Rodlike Molecular Forms: When 4-Cyanoresorcinol Meets the Carbosilane End Group Eduard Westphal, [a, b] Hugo Gallardo, [b] Giovanni Finoto Caramori, [b] Nerea Sebastiµn, [c] Maria-Gabriela Tamba, [c] Alexey Eremin,* [c] Susumu Kawauchi, [d] Marko Prehm, [a] and Carsten Tschierske* [a] Dedicated to Prof. Heinrich Lang on the occasion of his 60th birthday Abstract: Two isomeric achiral bent-core liquid crystals in- volving a 4-cyanoresorcinol core and containing a carbosilane unit as nanosegregating segment were synthesized and were shown to form ferroelectric liquid-crystalline phases. In- version 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 conse- quent 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 (SmCL s P S ) 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 carbo- silane groups and shows a randomized polar SmA phase (SmAP AR ) and ferroelectric polydomain SmC s P S 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-sym- metry breaking with formation of a conglomerate of macro- scopic chiral domains was observed in one of the SmC phases of CN1. These investigations contribute to the gener- al understanding of the development of polar order and chirality in soft matter. Introduction Multifunctional materials responding to magnetic or electrical fields, especially ferromagnetic and ferroelectric materials with long-range polarization of magnetic and electric dipoles, re- spectively, are of significant importance for the further devel- opment of technology, information storage, and information processing. In contrast to solid-state inorganic magnetic and ferroelectric materials, organic counterparts can be soft or even fluid, which provides them with the additional advantage of being easily processible, self-healing, and responsive to dif- ferent types of stimuli. [1–8] Especially liquid-crystalline (LC) or- ganic ferroelectrics combining molecular mobility with long- range order attract significant practical interest for microdis- plays, energy conversion, and information storage. [4–6] However, the softness of LC ferroelectrics requires sophisticated molecu- lar design to avoid randomization of polar order in the fluid state, which still remains a challenging task. It is just as impor- tant to know how structural modifications affect the molecular properties, which allows the development of more efficient materials. One important class of soft ferroelectrics is based on bent-core mesogens or banana-shaped LCs involving nonlinear units such as 1,3-disubstituted aromatics or other shape-persis- tent bent building blocks. [9–11] A small change of the molecular shape from linear, as in classical rodlike (calamitic) LCs, [4] to bent, in these bent-core mesogens, hampers molecular rota- tion around the mesogenic long axis, and provides polar order [a] Dr. E. Westphal, Dr. M. Prehm, Prof. Dr. C. Tschierske Institute of Chemistry, Organic Chemistry Martin Luther University Halle-Wittenberg Kurt-Mothes-Strasse 2, 06120 Halle/Saale (Germany) E-mail : carsten.tschierske@chemie.uni-halle.de [b] Dr. E. Westphal, Prof. Dr. H. Gallardo, Prof. Dr. G. F. Caramori Department of Chemistry Federal University of Santa Catarina 88040-900, Florianópolis (Brazil) [c] Dr. N. Sebastiµn, Dr. M.-G. Tamba, Dr. A. Eremin Department of Nonlinear Phenomena, Institute for Experimental Physics Otto von Guericke University Magdeburg Universitätsplatz 2, 39106 Magdeburg (Germany) E-mail: alexey.eremin@ovgu.de [d] Prof. Dr. S. Kawauchi Department of Organic & Polymeric Materials Tokyo Institute of Technology O-okayama, Meguro-ku, Tokyo 152-8552 (Japan) Supporting information and ORCID number from the author for this article are available on the WWW under http://dx.doi.org/10.1002/ chem.201503901. Chem. Eur. J. 2016, 22, 8181 – 8197 # 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 8181 Full Paper DOI: 10.1002/chem.201503901