Polyelectrolyte multilayer formation: electrostatics and short-range interactions

TL;DR

This study uses mean-field theory to analyze how electrostatic and short-range interactions influence the formation of polyelectrolyte multilayers during layer-by-layer deposition, highlighting the importance of short-range attraction.

Contribution

It provides a theoretical framework linking short-range attraction strength to multilayer stability and growth behavior, advancing understanding of multilayer assembly mechanisms.

Findings

Strong short-range attraction is crucial for multilayer formation.

Adsorbed amount decays with distance for weak attraction.

Stable multilayers form with sufficiently strong attraction.

Abstract

We investigate the phenomenon of multilayer formation via layer-by-layer deposition of alternating charge polyelectrolytes. Using mean-field theory, we find that a strong short-range attraction between the two types of polymer chains is essential for the formation of multilayers. The dependence of the required short-range attraction on the polymer charge fraction and salt concentration is calculated. For weak short-range attraction between any two adjacent layers, the adsorbed amount (per added layer) decays as the distance from the surface increases, until the chains stop adsorbing altogether. For strong short-range attraction, the adsorbed amount per layer increases after an initial decrease, and finally it stabilizes in the form of a polyelectrolyte multilayer that can be repeated many times.