Hydrogen bond-driven interactions between chitosan and biobased surfactants: A study of bulk behavior and surface adsorption

Abstract

This study explores the hydrogen bond-mediated association between chitosan (CHI) and alkyl polyglucoside (APG), a bio-based surfactant, in acidic conditions with varying ionic strengths. Unlike conventional polyelectrolyte-surfactant interactions that depend on electrostatic forces, the association in this system relies purely on non-ionic interactions. Using UV–visible spectroscopy, phase diagrams, and quartz crystal microbalance with dissipation monitoring (QCM-D), the bulk phase behavior and adsorption characteristics of CHI-APG mixtures on negatively charged surfaces was studied. Results demonstrate that APG concentration controls the phase behavior, with moderate levels inducing coacervate formation, while higher ionic strengths promote this coacervation through enhanced hydrogen bonding interactions. This shift leads to the formation of a phase-separated morphology, with micron-sized coacervate droplets observable in solution. Zeta potential measurements suggest that these droplets adopt a core–shell structure, characterized by a hydrophobic core due to the surfactant’s alkyl chains and a hydrophilic shell formed by chitosan. Additionally, the coacervation process significantly enhances the adsorption of CHI-APG complexes onto solid substrates, a feature with potential applications in targeted delivery and controlled release systems. Overall, this study provides critical insights into the design of bio-based, sustainable formulations and expands the understanding of hydrogen bond-driven, non-electrostatic coacervation, relevant for applications in cosmetics, biomedical coatings, and environmentally friendly materials.