Study of Physical Properties of Binary Mixtures of Two Nematogens

Abstract

We have reported different physical parameters of binary mixtures of p-ethoxyphenyl trans-4-butylcyclohexane carboxylate and 4′-n-pentyloxy-4-cyanobiphenyl, the two nematogenic compounds. The mixtures are prepared in four different compositions with X_50CB=0.213, 0.434, 0.626 and 0.818. Transition temperatures are determined by studying textures under a polarizing microscope. For all the compounds schlieren textures are observed. X-ray diffraction, optical birefringence study and density measurements have been carried out throughout the mesomorphic range. Only one mixture shows a cybotactic nematic phase. Apparent molecular lengths and order parameters are determined from X-ray studies and n₀, n_e and Δn from optical studies. Variation of all the parameters with temperature and concentration is discussed. Order parameters are compared with theoretical values.

Key Words:

• Binary mixtures
• X-ray Diffraction
• Order Parameters
• Optical birefringence