Theoretical Modeling of Chemical Equilibrium in Weak Polyelectrolyte Layers on Curved Nanosystems

Abstract

Surface functionalization with end-tethered weak polyelectrolytes (PE) is a versatile way to modify and control surface properties, given their ability to alter their degree of charge depending on external cues like pH and salt concentration. Weak PEs find usage in a wide range of applications, from colloidal stabilization, lubrication, adhesion, wetting to biomedical applications such as drug delivery and theranostics applications. They are also ubiquitous in many biological systems. Here, we present an overview of some of the main theoretical methods that we consider key in the field of weak PE at interfaces. Several applications involving engineered nanoparticles, synthetic and biological nanopores, as well as biological macromolecules are discussed to illustrate the salient features of systems involving weak PE near an interface or under (nano)confinement. The key feature is that by confining weak PEs near an interface the degree of charge is different from what would be expected in solution. This is the result of the strong coupling between structural organization of weak PE and its chemical state. The responsiveness of engineered and biological nanomaterials comprising weak PE combined with an adequate level of modeling can provide the keys to a rational design of smart nanosystems.

Role of pKA in Charge Regulation and Conformation of Various Peptide Sequences

“…Molecular simulations using coarse-grained models have been previously applied to study charge regulation in synthetic weak polyelectrolyte homopolymers, consisting of weak acid or weak base groups [ 8 ]. From these simulations we have learned that ionisation of weak polyelectrolytes increases upon an increase in pH but it is suppressed as compared to the ideal case, as a consequence of electrostatic repulsion between like-charged groups [ 8 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. This increase of ionisation is accompanied by expansion of the polyelectrolyte chain, resulting in a dramatic increase of the end-to-end distance or gyration radius.…”

Phase Behavior of Ion-Containing Polymers in Polar Solvents: Predictions from a Liquid-State Theory with Local Short-Range Interactions

“…It is foreseeable that by extending the present research to a DFT formulation, it could be possible to explore the rich structural properties of ion-containing polymers with dispersion interactions and end-tethered weak ion-containing polymers at interfaces. The study of weak ion-containing polymers that are confined in an interface is a challenging field, although a very interesting one [ 125 ].…”

Pushing the limits of nanopore transport performance by polymer functionalization

“…11 In regard to molecular transport in polymer-functionalized nanopores, confinement effects are particularly discussed in the context of charge regulation but also in the context of ligand binding constants. 12 But not only the nanopore structure and its functionalization determine transport performance in polymer-functionalized nanopores. The solution composition and the interaction of dissolved molecules or ions with the grafted molecules or polymers within the nanopore have to be considered.…”