Description of the fluctuating colloid-polymer interface

TL;DR

This paper investigates the surface fluctuations of colloid-polymer interfaces across different scales, revealing that bending rigidity is negative and diminishes near the critical point, aligning with simulation results.

Contribution

It introduces a comprehensive description of interface fluctuations incorporating bending rigidity, highlighting its negative value and critical behavior.

Findings

Bending rigidity of the interface is negative.

Bending rigidity approaches zero near the critical point.

Results agree with Monte Carlo simulations.

Abstract

To describe the full spectrum of surface fluctuations of the interface between phase-separated colloid-polymer mixtures from low scattering vector q (classical capillary wave theory) to high q (bulk-like fluctuations), one must take account of the interface's bending rigidity. We find that the bending rigidity is negative and that on approach to the critical point it vanishes proportionally to the interfacial tension. Both features are in agreement with Monte Carlo simulations.