# Manipulation of confined polyelectrolyte conformations through dielectric mismatch

## TL;DR

This study shows how dielectric mismatch influences the shape of confined polyelectrolytes, enabling reversible conformational changes that could be useful in biosensing and drug delivery.

## Contribution

It reveals the role of dielectric mismatch and surface polarization in controlling polyelectrolyte conformations within spherical cavities, introducing a new mechanism for conformational manipulation.

## Key findings

- Conformations switch between amorphous and four-fold symmetry based on dielectric mismatch.
- Surface polarization enhances counterion adsorption and affects chain morphology.
- Reversible conformational changes depend on cavity size, dielectric properties, and ion concentration.

## Abstract

We demonstrate that a highly charged polyelectrolyte confined in a spherical cavity undergoes reversible transformations between amorphous conformations to a four-fold symmetry morphology as a function of dielectric mismatch between the media inside and outside the cavity. Surface polarization due to dielectric mismatch exhibits an extra "confinement" effect, which are most pronounced within a certain range of the cavity radius and the electrostatic strength between the monomers and counterions and multivalent counterions. For cavities with a charged surface, surface polarization leads to an increased amount of counterions adsorbed in the outer side, further compressing the confined polyelectrolyte into a four-fold symmetry morphology. The equilibrium conformation of the chain is dependent upon several key factors including the relative permittivities of the media inside and outside the cavity, multivalent counterion concentration, cavity radius relative to the chain length, and interface charge density. Our findings offer insights into the effects of dielectric mismatch in packaging and delivery of polyelectrolytes across media with different relative permittivities. Moreover, the reversible transformation of the polyelectrolyte conformations in response to environmental permittivity allows for potential applications in biosensing and medical monitoring.