Issue 8, 2010

Nematic phases of bent-core mesogens

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.

Graphical abstract: Nematic phases of bent-core mesogens

Supplementary files

Article information

Article type
Paper
Submitted
06 Nov 2009
Accepted
23 Jan 2010
First published
02 Mar 2010

Soft Matter, 2010,6, 1704-1721

Nematic phases of bent-core mesogens

C. Keith, A. Lehmann, U. Baumeister, M. Prehm and C. Tschierske, Soft Matter, 2010, 6, 1704 DOI: 10.1039/B923262A

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