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Abstract
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Article Information:
λ-shaped Mesogenic Homologous Series with Polar Substituents: Synthesis, Characterization and Unusual Dielectric Behaviour
R. Manohar, A.K. Srivastava, P.B. Chand, A.K. Misra, A.K. Prajapati and M.C. Varia
Corresponding Author: Rajiv Manohar
Submitted: 2009 June, 26
Accepted: 2009 July, 18
Published: |
Abstract:
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A new l-shaped mesogenic homologous series with polar bromo and nitro substituent was
synthesized by fixing rigid 2-bromo-4-nitrophenylazo groups to a resorcinol moiety. 4-n-alkoxybenzoyl groups
esterify both the phenolic -OH groups. In the present series, methoxy and ethoxy derivatives are nonmesogenic,
n-propyloxy to n-octyloxy derivatives exhibit enantiotropic nematic mesophase. Smectic C (SmC)
mesophase commences from the n- octyloxy derivative as an enantiotropic phase and is retained up to the last
member synthesized. The effect of polar bromo and nitro substituent on mesomorphic properties is discussed.
In this paper, we also report the unusual dielectric behaviour of n-octyloxy and n-tetradecyloxy derivatives of
the present l-shaped mesogenic homologous series. The dielectric permittivity of the sample was found to be
unusually low in SmC phase in comparison to nematic phase. We have explained it on the basis of twoconformer
model, which can exist in SmC phase due to specific shape of the molecule. The model has been
supported by calculating activation energy of both the possible conformers from Arrhenius plot of relaxation
frequency versus temperature. There is a clear difference in the value of activation energy of both the
conformers as expected.
Key words: C. Differential scanning calorimetry (DSC), D. Dielectric properties, D. Phase transitions, , , ,
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Cite this Reference:
R. Manohar, A.K. Srivastava, P.B. Chand, A.K. Misra, A.K. Prajapati and M.C. Varia, . λ-shaped Mesogenic Homologous Series with Polar Substituents: Synthesis, Characterization and Unusual Dielectric Behaviour. Research Journal of Applied Sciences, Engineering and Technology, (2): Page No: 66-76.
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ISSN (Online): 2040-7467
ISSN (Print): 2040-7459 |
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