Determination of the orientational order parameter of the homologous series of 4-cyanophenyl 4-alkylbenzoate (n.CN) by different methods.
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.
Department of Physics, North Bengal University, Siliguri-734 013, India. mkdnbu@yahoo.com
Malay Kumar
MK
Das
Gautam
G
Sarkar
Banani
B
Das
Ratan
R
Rai
Neeraj
N
Sinha
D016880:Anisotropy; D001565:Benzoates / Q000737:chemistry*; D060328:Magnetic Phenomena; D009682:Magnetic Resonance Spectroscopy; D009570:Nitriles / Q000737:chemistry*; D055620:Optical Phenomena; D013696:Temperature; D014961:X-Ray Diffraction
D001565:Benzoates; D009570:Nitriles