Molecular‐Level Origin‐ of Polyethylene‐ Oxide‐–Chitosan Macromolecular Blend Stability Through a Network of Noncovalent Interactions

Polyethylene oxide (PEO) and chitosan (CS) are widely used polymeric building blocks in biodegradable materials, yet the molecular origin of their blend compatibility remains poorly defined. To clarify the noncovalent interactions that stabilize PEO–CS systems, we performed a comprehensive DFT study on representative oligomeric models in aqueous medium at the M06‑2X/cc‑pVDZ level. The optimized PEO–CS assembly exhibits a markedly favorable binding energy of −37.49 kcal/mol, confirming thermodynamic stability, while EDA reveals dominant electrostatic, exchange, and correlation contributions that overcome short‑range repulsion. Real‑space descriptors obtained from NCI, together with IGMH partitioning and Interaction Region Indicator isosurfaces, demonstrate that an extended network of O─H and N─H─O hydrogen bonds and van der Waals contacts links the ether oxygens of PEO with the hydroxyl and amino groups of CS. NBO and AIM analyses further quantify significant lone‑pair→antibonding charge transfer and weak‑to‑medium closed‑shell hydrogen bonding, while MESP shows donor and acceptor regions across the blend interface. Together, these results show that PEO–CS blend stability arises from a finely balanced, cooperative NCI framework rather than simple physical mixing, providing mechanistic insight to guide the rational design of next‑generation chitosan‑based macromolecular materials for biomedical, environmental, and energy‑related applications.