A model study of cooperative binding of ionic surfactants to oppositely charged flexible polyions

TL;DR

This paper introduces a statistical Monte Carlo model to analyze the cooperative binding of ionic surfactants to flexible polyions, highlighting the roles of electrostatic and hydrophobic interactions in binding behavior.

Contribution

A novel stochastic model incorporating ligand association and polyion flexibility to interpret surfactant-polyion binding experiments.

Findings

Model explains critical aggregation concentration.

Binding isotherms are consistent with experimental data.

Ligand association width influences binding behavior.

Abstract

A novel statistical model for the cooperative binding of monomeric ligands to a linear lattice is developed to study the interaction of ionic surfactant molecules with flexible polyion chain in dilute solution. Electrostatic binding of a ligand to a site on the polyion and hydrophobic associations between the neighboring bound ligands are assumed to be stochastic processes. Ligand association separated by several lattice points within defined width is introduced for the flexible polyion. Model calculations by the Monte Carlo method are carried out to investigate the binding behavior. The hypothesis on the ligand association and its width on the chain are of importance in determining critical aggregation concentration and binding isotherm. The results are reasonable for the interpretations of several surfactant-flexible polyion binding experiments. The implications of the approach are presented and discussed.