Polymers pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore

TL;DR

This paper develops a thermodynamic model for polymer mixtures to understand how non-penetrating polymers influence the partitioning of penetrating polymers into nanometer-sized pores, revealing complex dependencies on mixture composition.

Contribution

It introduces a novel equation of state for binary polymer mixtures and the concept of "polymers-pushing-polymers" to explain polymer partitioning behavior in pores.

Findings

Partitioning depends on mixture composition and pore-penetration penalty.

Non-penetrating polymers can enhance or diminish partitioning.

Two energy scales govern the complex partitioning behavior.

Abstract

We investigate polymer partitioning from polymer mixtures into nanometer size cavities by formulating an equation of state for a binary polymer mixture assuming that only one (smaller) of the two polymer components can penetrate the cavity. Deriving the partitioning equilibrium equations and solving them numerically allows us to introduce the concept of "polymers-pushing-polymers" for the action of non-penetrating polymers on the partitioning of the penetrating polymers. Polymer partitioning into a pore even within a very simple model of a binary polymer mixture is shown to depend in a complicated way on the composition of the polymer mixture and/or the pore-penetration penalty. This can lead to enhanced as well as diminished partitioning, due to two separate energy scales that we analyse in detail.