Investigation of miscibility, acoustical parameters and molecular interactions in PVA-PVP polymer blends through...

Water-soluble polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) blends are extensively used in pharmaceutical, paper, and food packaging industries. Miscibility of PVA/PVP blends was first indicated by positive values of interaction parameters, including Sun's parameter (α), ∆B, and Chee's constant (µ). Blend films were characterized using FESEM, XRD, and FT-IR spectroscopy. In order to analyze physio-chemical qualities, acoustical parameters were also examined. In comparison to pure PVA (8.6226 eV) and PVP (6.8726 eV), DFT studies showed a smaller HOMO-LUMO energy gap for the blend (6.8460 eV) indicates lower hardness and increased chemical softness, which correspond to higher chemical reactivity and reduced kinetic stability. These features facilitate intermolecular charge transfer and enhance polarizability within the blend. This was corroborated by global reactivity descriptors, which showed that the blend had higher global softness (0.1460 eV⁻¹) and lower chemical hardness (3.423 eV) than individual components. Thermodynamic examination of polymer blend revealed higher total thermal energy (387.351 kcal/mol), specific heat (118.969 cal/mol·K), and entropy (216.316 cal/mol·K), indicating structural improvements. The MESP map of PVP shows negative potential (red/orange region) around the carbonyl oxygen, the pyrrolidone nitrogen, and the PVA shows alternating positive (blue region) (H) and negative (O) regions, which may indicate the ability to form hydrogen bonds. When blended with PVP, the PVA forms additional positive and negative regions due to intermolecular interactions. QTAIM analysis further described hydrogen bonding: positive ∇²ρBCP and H_BCP values indicated weak electrostatic interactions, while favored interactions with negative H_BCP and positive ∇²ρBCP revealed partial covalency and medium-strength hydrogen bonds. Blend miscibility has been verified by bond energies calculated from QTAIM. In conclusion, molecular docking suggesting favorable interfacial interactions by showing increase binding energies (from - 1.93 to - 2.39 kcal/mol) for PVP with different PVA content. FTIR, XRD, and FESEM results confirm that PVA/PVP blends are miscible and DFT as well as docking provide qualitative insight into potential intermolecular interactions for flexible highlighting their possible application as sustainable and environmentally friendly polymer alternatives.

All quantum chemical calculations were performed with Gaussian 09 [23] using the B3LYP functional and 6-31G(d,p) basis set. Electronic properties, including the HOMO-LUMO gap, were computed via density functional theory [20]. Molecular geometries were visualized with Gauss View, and AIM analyses were carried out using AIMALL [25]. Molecular docking was conducted using AutoDock4.2.6.