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Issue 44, 2006
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Shape-persistent V-shaped mesogens—formation of nematic phases with biaxial order

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Abstract

A homologous series of shape-persistent V-shaped molecules has been designed to form the biaxial nematic phase. Phenyleneethynylene moieties are attached to a bent fluorenone unit to create an apex angle of about 90°, which is determined from the single crystal structure. Two mesogens, one symmetric and another unsymmetric, have been synthesized by attaching a cyano group to one or both of the peripheral phenyl units, respectively. These groups introduce local dipoles essential for the formation of the nematic phases. The tendency to form a crystalline phase is reduced by laterally substituted hexyloxy chains which allow the nematic phase to be supercooled to a glassy state. Two of the three fluorenone derivatives exhibit a transition from the uniaxial nematic to the biaxial nematic phase. This transition has an undetectably small transition enthalpy, but the X-ray diffraction, polarizing optical microscopy, and conoscopy reveal the presence of the biaxial order in the low temperature nematic phase.

Graphical abstract: Shape-persistent V-shaped mesogens—formation of nematic phases with biaxial order

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Supplementary files

Article information


Submitted
21 Apr 2006
Accepted
07 Aug 2006
First published
19 Sep 2006

J. Mater. Chem., 2006,16, 4326-4334
Article type
Paper

Shape-persistent V-shaped mesogens—formation of nematic phases with biaxial order

M. Lehmann, S. Kang, C. Köhn, S. Haseloh, U. Kolb, D. Schollmeyer, Q. Wang and S. Kumar, J. Mater. Chem., 2006, 16, 4326
DOI: 10.1039/B605718G

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