Soft core fluid in a quenched matrix of soft core particles: A mobile mixture in a model gel

TL;DR

This study develops a density-functional theory to analyze a binary soft core particle mixture in a quenched matrix, revealing complex interfacial phenomena like capillary condensation and wetting.

Contribution

It introduces an explicit density functional approach for quenched-annealed mixtures of soft particles, linking bulk condensation to surface wetting behaviors.

Findings

Matrix-induced condensation in bulk

Interfacial properties show capillary condensation and wetting effects

Effective external potentials describe quenched species influence

Abstract

We present a density-functional study of a binary phase-separating mixture of soft core particles immersed in a random matrix of quenched soft core particles of larger size. This is a model for a binary polymer mixture immersed in a crosslinked rigid polymer network. Using the replica `trick' for quenched-annealed mixtures we derive an explicit density functional theory that treats the quenched species on the level of its one-body density distribution. The relation to a set of effective external potentials acting on the annealed components is discussed. We relate matrix-induced condensation in bulk to the behaviour of the mixture around a single large particle. The interfacial properties of the binary mixture at a surface of the quenched matrix display a rich interplay between capillary condensation inside the bulk matrix and wetting phenomena at the matrix surface.