Unraveling Chitosan-Wood Fiber Noncovalent Interactions (NCIs) for Sustainable Composite Design

Trees are abundant in resources, and functionalization can endow wood with diverse properties, expanding its application potential. Chitosan is frequently utilized for functionalized wood, and various lignocellulose-chitosan composites with intricate structures, morphologies, and anisotropies can be produced through a bottom-up assembly. Nevertheless, the physical interactions among the components of lignocellulose and alkaline polysaccharides remain inadequately understood. This study systematically examined the intermolecular forces between chitosan and the principal components of lignocellulose, hemicellulose, and lignin to clarify the nature of their interactions. Through a combination of adsorption experiments, isotherm modeling, and density functional theory (DFT) simulations, distinct interaction mechanisms governing these systems were identified. Results reveal that chitosan adsorption on wood fibers is heterogeneous and results in multilayer structures with different binding affinities. Lignin exhibits monolayer adsorption dominated by electrostatic and hydrophobic interactions, while cellulose and xylan exhibit mixed monolayer-multilayer adsorption primarily driven by hydrogen bonding. These molecular-level insights offer a solid theoretical foundation for the design, self-assembly, and production of chitosan/lignocellulose composites, promoting the advancement of biobased materials with customized properties.