Phase Characterization and Study of Molecular Order of a Three-Ring Mesogen by (13)C NMR in Smectic C and Nematic Phases

Kalaivani, S and Narasimhaswamy, T and Das, Bibhuti B and Lobo, Nitin P and Ramanathan, KV (2011) Phase Characterization and Study of Molecular Order of a Three-Ring Mesogen by (13)C NMR in Smectic C and Nematic Phases. In: Journal of Physical Chemistry B, 115 (40). pp. 11554-11565.

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Abstract

Molecules exhibiting a thermotropic liquid-crystalline property have acquired significant importance due to their sensitivity to external stimuli such as temperature, mechanical forces, and electric and magnetic fields. As a result, several novel mesogens have been synthesized by the introduction of various functional groups in the vicinity of the aromatic core as well as in the side chains and their properties have been studied. In the present study, we report three-ring mesogens with hydroxyl groups at one terminal. These mesogens were synthesized by a multistep route, and structural characterization was accomplished by spectral techniques. The mesophase properties were studied by hot-stage optical polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. An enantiotropic nematic phase was noticed for lower homologues, while an additional smectic C phase was found for higher homologues. Solid-state high-resolution natural abundance (13)C NMR studies of a typical mesogen in the solid phase and in the mesophases have been carried out. The (13)C NMR spectrum of the mesogen in the smectic C and nematic phases indicated spontaneous alignment of the molecule in the magnetic field. By utilizing the two-dimensional separated local field (SLF) NMR experiment known as SAMPI4, (13)C-(1)H dipolar couplings have been obtained, which were utilized to determine the orientational order parameters of the mesogen.

Item Type:	Journal Article
Publication:	Journal of Physical Chemistry B
Publisher:	American Chemical Society
Additional Information:	Copyright of this article belongs to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility) Division of Physical & Mathematical Sciences > Physics
Date Deposited:	04 Nov 2011 09:42
Last Modified:	04 Nov 2011 09:42
URI:	http://eprints.iisc.ac.in/id/eprint/41821

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