Soft Confinement for Polymer Solutions

TL;DR

This study models soft confinement of polymers within vesicles, revealing shape transitions driven by polymer phase separation and spontaneous curvature, aligning with recent experimental observations.

Contribution

It introduces a combined phase field and self-consistent field theoretical approach to analyze vesicle shape transitions caused by enclosed polymer solutions.

Findings

Prolate to pear shape transition due to polymer domain structure

Re-entrant transition between prolate and dumbbell shapes with spontaneous curvature

Agreement with recent experimental results by Terasawa et al.

Abstract

As a model of soft confinement for polymers, we investigated equilibrium shapes of a flexible vesicle that contains a phase-separating polymer solution. To simulate such a system, we combined the phase field theory (PFT) for the vesicle and the self-consistent field theory (SCFT) for the polymer solution. We observed a transition from a symmetric prolate shape of the vesicle to an asymmetric pear shape induced by the domain structure of the enclosed polymer solution. Moreover, when a non-zero spontaneous curvature of the vesicle is introduced, a re-entrant transition between the prolate and the dumbbell shapes of the vesicle is observed. This re-entrant transition is explained by considering the competition between the loss of conformational entropy and that of translational entropy of polymer chains due to the confinement by the deformable vesicle. This finding is in accordance with the recent experimental result reported by Terasawa, et al.