Wetting in mixtures of colloids and excluded-volume polymers from density functional theory

TL;DR

This study uses density functional theory to analyze wetting behavior in colloid-polymer mixtures, revealing a first-order wetting transition with prewetting, contrasting previous models, and emphasizing the need for accurate theoretical descriptions.

Contribution

It introduces a microscopic density functional theory for colloid-polymer mixtures that captures wetting phenomena not explained by earlier models.

Findings

Polymer-rich phase wets a hard wall, contrary to previous models.

Wetting transition is first order and involves prewetting.

No layering transitions observed in partial wetting regime.

Abstract

We use a microscopic density functional theory based on Wertheim's first order thermodynamic perturbation theory to study wetting behavior of athermal mixtures of colloids and excluded-volume polymers. In opposition to the wetting behavior of the Asakura-Oosawa-Vrij model we find the polymer-rich phase to wet a hard wall. The wetting transition is of the first order and is accompanied by the prewetting transition. We do not find any hints for the layering transitions in the partial wetting regime. Our results resemble the wetting behavior in athermal polymer solutions. We point out that an accurate, monomer-resolved theory for colloid-polymer mixtures should incorporate the correct scaling behavior in the dilute polymer regime and an accurate description of the reference system.