Structure of Colloid-Polymer Suspensions

TL;DR

This paper analyzes the microscopic structure of colloid-polymer suspensions, revealing how polymer size influences depletion layers and phase behavior through integral equation theory.

Contribution

It introduces a detailed theoretical framework for understanding structural correlations in colloid-polymer mixtures, accounting for polymer size and conformational effects.

Findings

Depletion layers exhibit two distinct length scales.

Polymer size significantly affects phase stability.

Structural correlations depend on polymer conformations.

Abstract

We discuss structural correlations in mixtures of free polymer and colloidal particles based on a microscopic, 2-component liquid state integral equation theory. Whereas in the case of polymers much smaller than the spherical particles the relevant polymer degree of freedom is the center of mass, for polymers larger than the (nano-) particles conformational rearrangements need to be considered. They have the important consequence that the polymer depletion layer exhibits two widely different length scales, one of the order of the particle radius, the other of the order of the polymer radius or the polymer density screening length in dilute or semidilute concentrations, respectively. Their consequences on phase stability and structural correlations are discussed extensively.