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Nematic phases of bent-core mesogens

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TLDR
In this article, a temperature dependent stepwise transition from cybotactic nematic phases to different types of non-polar and tilted smectic phases (SmC(I) and SmC(II)) is observed with a mesophase composed of elongated, but not yet fused cybactic clusters (CybC) as an intermediate state of this transition.
Abstract
Bent-core mesogens derived from 4-cyanoresorcinol with terminal alkyl chains have been synthesized and investigated by polarizing microscopy, XRD and electro-optical methods. Short chain compounds have exclusively nematic phases which can be cooled to ambient temperature. These nematic phases are similar to ordinary nematic phases with only nearest neighbour correlation (N) whereas long chain compounds form SmC-type cybotactic clusters and these cybotactic nematic phases (NcybC) can be regarded as strongly fragmented SmC phases. The chain length dependent as well as temperature dependent structural transition from N to NcybC is continuous and associated with a change of the position and intensity of the small angle scattering in the XRD patterns. Moreover, a temperature dependent stepwise transition from cybotactic nematic phases to different types of non-polar and tilted smectic phases (SmC(I) and SmC(II)) is observed with a mesophase composed of elongated, but not yet fused cybotactic clusters (CybC) as an intermediate state of this transition. This improves the understanding of the nature and special properties of the nematic phases formed by bent-core molecules as well as their transition to smectic phases and it paves the way to new materials with spontaneous or field-induced biaxial nematic phases at ambient temperatures.

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Journal ArticleDOI

Microrheology to probe smectic clusters in bent-core nematic liquid crystals.

TL;DR: The results show that the directional shear modulus of 16OCH3, just above the SmA to N phase transition temperature, is strikingly different than that of 8O CH3, owing to the smectic clusters.
Journal ArticleDOI

Single-component room-temperature discotic nematic liquid crystals formed by introducing an attraction-enhancing in-plane protrusion onto the hexa(phenylethynyl)benzene core

TL;DR: In this article, a single component room-temperature discotic nematics have been achieved within large temperature ranges by introducing an attractionenhancing protrusion onto hexa(phenylethynyl)benzenes.
Journal ArticleDOI

Effect of methoxy group instead of polar group in the nematic phase of four-ring bent-core liquid crystals

TL;DR: In this paper, two achiral four-ring bent-core liquid crystal possessing an alkoxy chain at one end of the molecules and methoxy group at the other end are investigated by using the optical polarizing microscope, electro-optical studies, and dielectric spectroscopy.
Journal ArticleDOI

Bent-shaped liquid crystals based on 4-substituted 3-hydroxybenzoic acid central core – Part II

TL;DR: In this article, the mesomorphic properties of 3-hydroxybenzoic acid central core were compared with 4-substituted resorcinol-based materials, taking into account also previously published derivatives.
References
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Journal ArticleDOI

Bent-core liquid crystals: polar order, superstructural chirality and spontaneous desymmetrisation in soft matter systems

TL;DR: An overview on the recent developments in the field of liquid crystalline bent-core molecules (so-called banana liquid crystals) is given in this article, dealing with general aspects of the systematisation of the mesophases, development of polar order and chirality in this class of LC systems and explaining some general structure-property relationships.
Journal ArticleDOI

Bent-Core Liquid Crystals: Their Mysterious and Attractive World

TL;DR: In this article, structural and properties of liquid crystalline phases formed by bent-core molecules are reviewed and the most attractive properties of this new class of liquid crystals are in polarity and chirality, despite being formed from achiral molecules.
Journal ArticleDOI

Thermotropic biaxial nematic liquid crystals.

TL;DR: Polarized microscopy and conoscopy indicate that liquid crystal mesogens based on a nonlinear oxadiazole unit that exhibit nematic phases near 200 degrees C are biaxial nematics, and unambiguous and quantitative evidence for biaXiality is achieved using 2H NMR spectroscopy.
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