Optical studies of a liquid crystalline compound 6O.6

Abstract

A detailed optical study for a Schiff's base liquid crystalline nO.m compound (6O.6) is reported in this article. The phase transition temperatures for the compound were investigated using a polarising microscopy and differential scanning calorimetry (DSC). Refractive index studies were conducted using the thin prism method with the 633 nm line from a He–Ne laser. The order parameters of the compound were calculated from the refractive index data. Order parameters calculated by two methods, namely, direct extrapolation method and modified Vuks’ method were found to be in close agreement. The normalised polarisabilities for extraordinary and ordinary rays and their ratio for the sample were also calculated. The order parameters are found to be reasonably high and the trend shown by normalised polarisabilities substantiates the correctness of our results. From the methods we adopted, the order parameters and the normalised polarisabilities could be determined directly from the refractive index measurements without doing the density studies. Both these methods are found to be highly suitable for the calculation of order parameters of liquid crystalline compounds having high clearing temperature where density studies are difficult and hazardous.

Keywords:

• nO.m
• thin prism
• birefringence
• order parameter

Acknowledgements

K.D. Thingujam acknowledges the financial assistance from NIT Silchar, Assam, India.