Free Solution Electrophoresis of Homopolyelectrolytes

TL;DR

This study uses computer simulations to explore how polyelectrolytes behave under electric fields in multivalent salt solutions, revealing a size-dependent unfolding transition that can aid in separating long charged polymers.

Contribution

It demonstrates the electric field-induced unfolding transition of polyelectrolytes in salt solutions and its dependence on chain length, suggesting a new method for polymer separation.

Findings

Chain unfolds and aligns with electric field at a critical field strength.

Unfolding electric field scales as V^{-1/2} with chain volume.

Electrophoretic mobility increases significantly during unfolding.

Abstract

We investigate the behavior of single polyelectrolytes in multivalent salt solutions under the action of electric fields through computer simulations. The chain is unfolded in a strong electric field and aligned parallel to the field direction, and the chain size shows a sigmoidal transition. The unfolding electric field $E^*$ depends on the salt concentration and scales as $V^{-1/2}$ with $V$ being the ellipsoidal volume occupied by the chain. The magnitude of the electrophoretic mobility of chain drastically increases during the unfolding. The fact that $E^*$ depends on the chain length provides a plausible mechanism to separate long charged homopolymers by size in free solution electrophoresis via the unfolding transition of globule polyelectrolytes condensed by multivalent salt.