Colloid-polymer mixtures in the protein limit

TL;DR

This paper investigates the phase separation and effective interactions in colloid-polymer mixtures in the protein limit, revealing distinct behaviors for ideal and interacting polymers and emphasizing the importance of many-body effects.

Contribution

It provides a detailed analysis of phase behavior and interactions in the protein limit, highlighting the limitations of pair potentials and the role of many-body contributions.

Findings

Critical colloid packing fraction approaches zero for ideal polymers.

Universal binodal governs behavior for interacting polymers.

Depletion interactions require many-body considerations.

Abstract

We computed the phase-separation behavior and effective interactions of colloid-polymer mixtures in the "protein limit", where the polymer radius of gyration is much larger than the colloid radius. For ideal polymers, the critical colloidal packing fraction tends to zero, whereas for interacting polymers in a good solvent the behavior is governed by a universal binodal, implying a constant critical colloid packing fraction. In both systems the depletion interaction is not well described by effective pair potentials but requires the incorporation of many-body contributions.