Order Parameters from Magnetic Susceptibility Measurements on Some Nematogens

The diamagnetic susceptibility of three alkoxyphenyl trans-4-alkyl cyclohexane carboxylates and p-cyanophenyl trans-4-pentyl cyclohexane carboxylate are reported as a function of temperature in the solid, nematic and isotropic phases. Assuming that the molecules are effectively axially symmetric, the temperature dependence of orientational order parameter (P 2) has been investigated from the anisotropy of the susceptibility at different temperatures. The values of (P 2) agree reasonably well with the predictions from Maier and Saupe theory except near the clearing point where the values of (P 2) are lower than theoretical prediction, whereas (P 2) values obtained from X-ray diffraction studies show good agreement with theoretical values. The possible cause of this discrepancy has been discussed.