Neutral and Charged Polymers at Interfaces

TL;DR

This review discusses the fundamental concepts, recent advances, and detailed behaviors of neutral and charged polymers at interfaces, emphasizing adsorption, surface interactions, and the effects of polymer flexibility and charge.

Contribution

It provides a comprehensive overview of the current understanding of polymer adsorption at interfaces, including recent progress and detailed analysis of semi-flexible and charged polymers.

Findings

Charged polymers (polyelectrolytes) exhibit unique adsorption behaviors due to water solubility.

Surface tension and polymer surface excess are influenced by polymer structure and interactions.

Grafted polymer brushes show distinct properties for neutral and charged cases.

Abstract

Chain-like macromolecules (polymers) show characteristic adsorption properties due to their flexibility and internal degrees of freedom, when attracted to surfaces and interfaces. In this review we discuss concepts and features that are relevant to the adsorption of neutral and charged polymers at equilibrium, including the type of polymer/surface interaction, the solvent quality, the characteristics of the surface, and the polymer structure. We pay special attention to the case of charged polymers (polyelectrolytes) that have a special importance due to their water solubility. We present a summary of recent progress in this rapidly evolving field. Because many experimental studies are performed with rather stiff biopolymers, we discuss in detail the case of semi-flexible polymers in addition to flexible ones. We first review the behavior of neutral and charged chains in solution. Then, the adsorption of a single polymer chain is considered. Next, the adsorption and depletion processes in the many-chain case are reviewed. Profiles, changes in the surface tension and polymer surface excess are presented. Mean-field and corrections due to fluctuations and lateral correlations are discussed. The force of interaction between two adsorbed layers, which is important in understanding colloidal stability, is characterized. The behavior of grafted polymers is also reviewed, both for neutral and charged polymer brushes.