From Octopus to Dendrite - Semiflexible Polyelectrolyte Brush Condensates in Trivalent Counterion Solution

TL;DR

This study explores how trivalent counterions influence the morphology and dynamics of semiflexible polyelectrolyte brush condensates, revealing distinct structures and mobility patterns depending on chain rigidity and ionic conditions.

Contribution

It demonstrates the formation of octopus-like micelles and dendritic condensates driven by counterion interactions and chain stiffness, providing new insights into polyelectrolyte behavior.

Findings

Flexible chains form surface micelles under trivalent ions.

Rigid chains develop fractal dendritic condensates with slow relaxation.

Dendritic condensates exhibit quasi-one-dimensional ion diffusion.

Abstract

Interplay between counterion-mediated interaction and stiffness inherent to polymer chain can bring substantial complexity to the morphology and dynamics of polyelectrolyte brush condensates. Trivalent counterions induce collapse of flexible polyelectrolyte brushes, over a certain range of grafting density, into octopus-like surface micelles; however, if individual chains are rigid enough, the ion-mediated local nematic ordering assembles the brush chains into fractal-like dendritic condensates whose relaxation dynamics is significantly slower than that in the surface micelles. Notably, the trivalent ions condensed in the dendritic condensates are highly mobile displaying quasi-one-dimensional diffusion in parallel along the dendritic branches. Our findings in this study are potentially of great significance to understanding the response of cellular organization such as chromosomes and charged polysaccharides on membranes to the change in ionic environment.