A Simple Free Energy for the Isotropic-Nematic Phase Transition of Rods

Abstract EN

A free energy expression is proposed that describes the isotropic-nematic binodal concentrations of hard rods.

A simple analytical form for this free energy was yet only available using a Gaussian trial function for the orientation distribution function (ODF), leading, however, to a significant deviation of the predicted binodals.

The new free energy proposed here is based upon a rationalized correction to the orientational and packing entropies when using the Gaussian ODF.

In combination with Parsons-Lee theory or scaled particle theory, it enables describing the isotropic-nematic phase coexistence concentrations of rods accurately using the simple Gaussian ODF for a wide range of aspect ratios.