Density functional theory and demixing of binary hard rod-polymer mixtures

TL;DR

This paper develops a density functional theory for binary mixtures of hard rods and polymers, analyzing their phase separation behavior and how it depends on chain length and packing fraction.

Contribution

It combines existing functionals to model rod-polymer mixtures and investigates the demixing transition, highlighting effects of chain length on phase behavior.

Findings

Phase boundary broadens with increasing chain length.

Critical packing fraction decreases as chain length increases.

Shift of the critical point is most noticeable for short chains.

Abstract

A density functional theory for a mixture of hard rods and polymers modeled as chains built of hard tangent spheres is proposed by combining the functional due to Yu and Wu for the polymer mixtures [J. Chem. Phys. {\bf 117}, 2368 (2002)] with the Schmidt's functional [Phys. Rev. E {\bf 63}, 50201 (2001)] for rod-sphere mixtures. As a simple application of the functional, the demixing transition into polymer-rich and rod-rich phases is examined. When the chain length increases, the phase boundary broadens and the critical packing fraction decreases. The shift of the critical point of a demixing transition is most noticeable for short chains.