Charged rosettes at high and low ionic strengths

TL;DR

This paper investigates the formation of rosette structures in polyelectrolyte-macroion complexes, analyzing how ionic strength influences their morphology and transition characteristics through scaling theories.

Contribution

It introduces scaling theories for rosette formation under both short-range and long-range electrostatic interactions, highlighting the robustness and transition differences.

Findings

Rosette structures are robust against ionic strength variations.

Transition to rosette structures is discontinuous for short-range interactions.

Transition is continuous for long-range interactions.

Abstract

The complexation between a semiflexible polyelectrolyte and an oppositely charged macroion leads to a multitude of structures ranging from tight complexes with the chain wrapped around the macroion to open multileafed rosette-like complexes. Rosette structures, expected to occur for short-ranged attractions between the macroion and the chain, have now also been seen in recent Monte Carlo simulations with long-range (unscreened) interactions [Akinchina and Linse Macromolecules 2002, 35, 5183]. The current study provides scaling theories for both cases and shows that rosette structures are indeed quite robust against changes in the ionic strength. However, the transition from the wrapped to the rosette configuration has a dramatically different characteristics: The short-range case leads to a strongly discontinuous transition into a rosette with large leaves whereas the long-range case occurs in a continuous fashion. We provide the complete diagram of states for both cases.