Model of hard spheroplatelets near a hard wall

TL;DR

This paper models the behavior of hard spheroplatelets near a wall using Onsager theory, deriving analytical expressions for surface properties and orientation profiles, highlighting the conditions for biaxiality near the surface.

Contribution

It introduces an analytical model for spheroplatelets near a wall, capturing surface tension, entropy, and orientation profiles within the low-density Onsager approximation.

Findings

Preferred orientation of molecules is perpendicular to the wall.

Biaxiality near the wall occurs only if the bulk phase is biaxial.

Analytical expressions for surface tension and density profiles are derived.

Abstract

A system of hard spheroplatelets near an impenetrable wall is studied in the low-density Onsager approximation. Spheroplatelets have optimal shape between rods and plates, and the direct transition from the isotropic to biaxial nematic phase is present. A simple local approximation for the one-particle distribution function is used. Analytical results for the surface tension and the entropy contributions are derived. The density and the order-parameter profiles near the wall are calculated. The preferred orientation of the short molecule axes is perpendicular to the wall. Biaxiality close to the wall can appear only if the phase is biaxial in the bulk.