Gautam Sarkar

Publications (3)3.55 Total impact

• Article: Determination of the orientational order parameter of the homologous series of 4-cyanophenyl 4-alkylbenzoate (n.CN) by different methods.

  Malay Kumar Das, Gautam Sarkar, Banani Das, Ratan Rai, Neeraj Sinha
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  ABSTRACT: The orientational order parameters of a homologous series of 4-cyanophenyl 4-alkylbenzoates have been determined at different temperatures from (13)C-NMR, x-ray diffraction, optical birefringence, high resolution density and diamagnetic susceptibility anisotropy measurements. To determine the temperature dependence of the orientational order parameter from the (13)C chemical shift values, the two-dimensional polarization inversion spin exchange at the magic angle (PISEMA) method was also used for the measurement of (13)C-(1)H dipolar couplings at different sites in the oriented phase. The nematic order parameters determined from each of these methods have been compared. Apart from a slight shift in their values their trends with temperature are very similar. The differences among the results obtained by these five different methods have been discussed. From the high resolution density data, the values of the critical exponents near the T(N-I) transition are found to lie between the Ising model and tricritical behaviour.
  Journal of Physics Condensed Matter 03/2012; 24(11):115101. · 2.55 Impact Factor
• Article: Structural investigations of a non calamitic shaped liquid crystalline compound showing unusual phases

  Gautam Sarkar, Banani Das, Malay Kumar Das, Ute Baumaister, Wolfgang Weissflog
  Mol. Cryst. Liq. Crys. 01/2011; 54:188.
• Article: Comparison of the orientational order parameters determined from X-ray diffraction and 13C NMR studies of a hockey stick-shaped compound

  Gautam Sarkar, Malay Kumar Das, Ranjit Paul, Banani Das, Wolfgang Weissflog
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  ABSTRACT: Orientational order parameters (OOP's) have been determined in the Smectic A, Smectic C1 and Smectic C2 phases of a hockey stick-shaped compound from X-ray diffraction measurements and compared with NMR measurements. While the OOP values from NMR measurements abruptly drop at the Smectic C1 to Smectic C2 transition, those determined from X-ray diffraction measurements decreases sharply at the Smectic A to Smectic C1 transition. This drop in the OOP values from X-ray measurements has been explained using a model where the molecular director is randomly oriented in a cone about the smectic layer normal. OOP's from X-ray diffraction and NMR measurements have been successfully fitted with McMillan's theory, after necessary correction to the potential, incorporating tilt angles, for three homologues with n = 10, 11 and 12. The temperature dependences of the optical birefringence, dielectric anisotropy and OOP values determined from birefringence measurements of compound 11 are also reported.
  Phase Transitions 06/2009; 82(6):433-443. · 1.01 Impact Factor