Sequence disorder-induced first order phase transition in confined polyelectrolytes

TL;DR

This paper models a flexible polyelectrolyte with sequence disorder and demonstrates that disorder induces a first order phase transition, significantly affecting the chain's localization and the system's pressure between surfaces.

Contribution

It introduces a statistical mechanical model incorporating sequence disorder effects, revealing a disorder-induced first order phase transition in confined polyelectrolytes.

Findings

Sequence disorder enhances chain localization.

A first order phase transition occurs at a critical spacing.

Pressure changes abruptly from negative to positive.

Abstract

We consider a statistical mechanical model of a generic flexible polyelectrolyte, comprised of identically charged monomers with long range electrostatic interactions, and short-range interactions quantified by a disorder field along the polymer contour sequence, which is randomly quenched. The free energy and the monomer density profile of the system for no electrolyte screening are calculated in the case of a system composed of two infinite planar bounding surfaces with an intervening oppositely charged polyelectrolyte chain. We show that the effect of the contour sequence disorder, mediated by short-range interactions, leads to an enhanced localization of the polyelectrolyte chain and a first order phase transition at a critical value of the inter-surface spacing. This phase transition results in an abrupt change of the pressure from negative to positive values, effectively eliminating polyelectrolyte mediated bridging attraction.