Effect of polymer-polymer interactions on the surface tension of colloid-polymer mixtures

TL;DR

This study investigates how polymer-polymer interactions influence the surface tension and interface width in phase-separated colloid-polymer mixtures, revealing that interactions lead to lower surface tension and narrower interfaces.

Contribution

It provides a theoretical analysis of the effects of polymer-polymer interactions on surface tension using the square gradient approximation, extending understanding beyond ideal polymer models.

Findings

Interacting polymers reduce interface width compared to ideal polymers.

Surface tension is lower in systems with polymer-polymer interactions.

Depletion potential between colloids is shorter-ranged with interacting polymers.

Abstract

The density profile and surface tension for the interface of phase-separated colloid-polymer mixtures have been studied in the framework of the square gradient approximation for both ideal and interacting polymers in good solvent. The calculations show that in the presence of polymer-polymer excluded volume interactions the interfaces have lower widths and surface tensions compared to the case of ideal polymers. These results are a direct consequence of the shorter range and smaller depth of the depletion potential between colloidal particles induced by interacting polymers.