Multifunctional chitosan modified waterborne polyurethane films: An integrated experimental and molecular docking study for structure interaction correlation.

Chitosan-modified waterborne polyurethane (CS@WBP) films were synthesized through a prepolymer approach using butanediol (BDO), isophorone diisocyanate (IPDI), and dimethylol propionic acid (DMPA), followed by the incorporation of chitosan to introduce additional functional amino and hydroxyl groups. A conventional BDO-chain-extended waterborne polyurethane (BDO@WBP) was also prepared as a reference system to distinguish the effects of conventional diol chain extension from those associated with CS incorporation. The resulting system (CS@WBP) formed homogeneous aqueous dispersions and uniform, defect-free films, demonstrating good compatibility between CS and the polyurethane matrix. FTIR and NMR analyses confirmed the successful formation of the polyurethane network and the incorporation of CS through intermolecular interactions. DLS analysis revealed an average hydrodynamic particle size of approximately 188.5 nm with a reasonably uniform particle size distribution, indicating satisfactory dispersion characteristics. Morphological analyses (OM and FE-SEM) showed homogeneous, continuous film surfaces, while XRD confirmed a semi-crystalline structure. The films exhibited moderate hydrophilicity (contact angle ~43-49°) and enhanced thermal stability with increased char formation (~10-12%). Mechanical analysis indicated that the developed films are soft and flexible (Young's modulus: 2.11 MPa; elongation at break: 22.4%), making them suitable for functional film applications. In comparison, the BDO@WBP reference exhibited a slightly larger hydrodynamic particle size (210.3 nm) and lower film-forming integrity under the investigated formulation conditions, with the film fracturing during specimen preparation for tensile testing. Molecular docking studies demonstrated favorable interactions with selected bacterial target proteins, particularly DNA gyrase (-6.9 kcal mol-1), providing theoretical support for potential antimicrobial functionality. Unlike conventional studies focusing solely on material characterization, this work integrates comprehensive experimental characterization with molecular docking to establish a structure-interaction relationship at the molecular level. Overall, the developed CS@WBP films represent a promising multifunctional polymer system for sustainable applications. However, further experimental antimicrobial evaluation is required to validate the computational predictions and establish their practical biological performance.