Molecular Design of Nonchiral Bent-Core Liquid Crystals with Antiferroelectric Properties

Abstract

Novel bent-core (banana-shaped) liquid crystals without Schiff-base units have been synthesized and investigated by polarized light optical microscopy, differential scanning calorimetry, X-ray scattering, and electrooptical investigations. These molecules are 4-(4-alkylbenzoyloxy)benzoates and 4-(4-alkoxybenzoyloxy)benzoates of resorcinol, 3,4′-dihydroxybiphenyl, and 4,4′′-dihydroxy-1,1′:3′,1′′-terphenyl. Three different mesophases were found depending on the molecular structure and the length of the terminal alkyl chains: a rectangular columnar phase, a highly ordered low-temperature mesophase, and an antiferroelectric switchable fluid smectic mesophase designated as SmCP A . The influence of the molecular structure on the occurrence of the SmCP A phase was investigated. The spontaneous polarization of these molecules is quite high (P S ) 500-700 nC cm -2 ) and specially those molecules with long alkyl chains and short bent-core structures have low melting points and broad regions of this switchable mesophase. Furthermore, first examples of antiferroelectric switchable bent-core molecules with semifluorinated terminal chains will be described.

New H‐Bonded Complexes and Their Supramolecular Liquid‐Crystalline Organizations

“…The complexes show two absorptions around 1950 and 2500 cm -1 , which correspond to the N···H-O interaction, whereas carboxylic acid dimers exhibit a band at 2650 cm -1 (O-H). Likewise, bands corresponding to the C=O absorption of acid dimers (around [6] C 97 SmC 139 I B14 [6] C 1683 cm -1 ) were not detected for the complexes. Furthermore, variable-temperature IR spectra reveal that dissociation of the self-assembly is not observed either in the solid or the mesophase.…”

Field‐Induced Switching of Chirality in Undulated Ferroelectric and Antiferroelectric SmCP Phases Formed by Bent‐Core Mesogens

“…We investigated eight homologues of a new series of bent-core mesogens in which the outer linking groups are reversed compared to isomeric compounds reported in the literature. [10] We found that all the homologues form a polar tilted smectic C (SmCP) phase with undulated smectic layers. From electrooptical experiments it follows that the short-chain members possess an antiferroelectric ground state while the longchain members are ferroelectric.…”

Electric-field-induced phase transitions in bent-core mesogens determined by x-ray diffraction

“…The synthesis of NG75 together with a preliminary phase characterization has been published in Ref. [27] (the material was named 3/14 in that study). Details of the synthesis of PAT11 and NG126 are reported in [19].…”