Demixing in athermal mixtures of colloids and excluded-volume polymers from a density functional theory

TL;DR

This study uses density functional theory to analyze how chain length affects the interfacial properties of colloid-polymer mixtures, revealing increased surface tension and interfacial width with longer chains, and oscillatory density profiles.

Contribution

It provides a theoretical framework for understanding the influence of polymer chain length on interfacial properties in colloid-polymer mixtures.

Findings

Interfacial tension increases with chain length.

Oscillations observed in density profiles near interfaces.

Interfacial width grows with chain length and varies for different segments.

Abstract

We study the structure and interfacial properties of model athermal mixtures of colloids and excluded volume polymers. The colloid particles are modeled as hard spheres whereas the polymer coils are modeled as chains formed from tangentially bonded hard spheres. Within the framework of the nonlocal density functional theory we study the influence of the chain length on the surface tension and the interfacial width. We find that the interfacial tension of the colloid-interacting polymer mixtures increases with the chain length and is significantly smaller than that of the ideal polymers. For certain parameters we find oscillations on the colloid-rich parts of the density profiles of both colloids and polymers with the oscillation period of the order of the colloid diameter. The interfacial width is few colloid diameters wide and also increases with the chain length. We find the interfacial width for the end segments to be larger than that for the middle segments and this effect is more pronounced for longer chains.