Orientational Ordering of a Nematogen from X-Ray Diffraction Studies

Abstract

In this paper we have reported the results of X-ray diffraction studies on the nematic phase of 4-ethoxyphenyl trans-4′-propyl cyclohexane carboxylate at different temperatures. We have analyzed the experimental data to determine the orientational distribution function and hence to calculate the oricntational order parameters (P ₂) and (P ₄). The experimental order parameter values disagree with the Maier-Saupe mean field theory, but are in excellent agreement with the continuum theory of T. E. Faber. The possible causes for deviation from mean field model have been discussed. The molecules also form association with apparent molecular length of about 1.5 times their actual length.

Key Words:

• nematogens
• x-ray diffraction
• order parameter
• molecular association