Nematic Ordering in nOCB Series from Molecular Polarizabilities

Abstract

The molecular polarizabilities (α₀, α_e,) of the four members of the homologous series of cyano-alkyloxy-biphenyl (C_nH_2n+1.O.φ.φ.CN for n = 5 to 8) in the nematic range have been calculated using two different internal field models. The additive rule of bond polarizabilities has been adopted to get the mean polarizability (α) and the principal molecular polarizability anisotropy (α₁ - α₁) values for these compounds. The orientational order parameters have been calculated from these results. The ordering exhibits an odd-even alternation along the series. The results have been compared with different theories. Possible causes for deviation from the theories have been discussed. Besides the relative stabilities of the alkyloxy cyano biphenyls have also been discussed in terms of the molecular parameters.

Key Words:

• molecular polarizability
• order parameter
• odd-even effect