The local phase transitions of the solvent in the neighborhood of a solvophobic polymer at high pressures

TL;DR

This study models how solvent phase transitions near a solvophobic polymer are influenced by changes in polymer-solvent repulsion and high bulk pressure, revealing coil-globule transitions linked to local solvent evaporation or condensation.

Contribution

It introduces a mean-field theoretical framework to analyze local solvent phase transitions around a solvophobic polymer at high pressures.

Findings

Polymer undergoes coil-globule transition with solvent evaporation.

Polymer transitions from globule to coil with solvent condensation.

High pressure influences local solvent density and phase behavior.

Abstract

We investigate local phase transitions of the solvent in the neighborhood of a solvophobic polymer chain which is induced by a change of the polymer-solvent repulsion and the solvent pressure in the bulk solution. We describe the polymer in solution by the Edwards model, where the conditional partition function of the polymer chain at a fixed radius of gyration is described by a mean-field theory. The contributions of the polymer-solvent and the solvent-solvent interactions to the total free energy are described within the mean-field approximation. We obtain the total free energy of the solution as a function of the radius of gyration and the average solvent number density within the gyration volume. The resulting system of coupled equations is solved varying the polymer-solvent repulsion strength at high solvent pressure in the bulk. We show that the coil-globule (globule-coil) transition occurs accompanied by a local solvent evaporation (condensation) within the gyration volume