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2009 (Vol. 1, Issue: 2)
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 

Key words:  C. Differential scanning calorimetry (DSC), D. Dielectric properties, D. Phase transitions, , , ,
Vol. 1 , (2): Page No: 66-76
Submitted Accepted Published
2009 June, 26 2009 July, 18
Abstract:

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.
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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, 2009. λ-shaped Mesogenic Homologous Series with Polar Substituents: Synthesis, Characterization and Unusual Dielectric Behaviour.  Research Journal of Applied Sciences, Engineering and Technology, 1(2): Page No: 66-76.
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ISSN (Online):  2040-7467
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