Bio-based multifunctional films via PDMS and natural oil surface engineering

Hybrid films were developed using carboxymethyl cellulose (CMC), non-isocyanate hydroxyurethane (NIHU), and lignosulfonate (LS) as the base matrix, followed by surface engineering through spray coating of polydimethylsiloxane (PDMS), silicone oil (SO), and tea tree oil (TTO) onto the film surface. Structural and morphological analyses, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and atomic force microscopy (AFM), confirmed both the integrity of the matrix and the successful deposition of a PDMS-derived hydrophobic layer enriched with SO for flexibility and TTO for bioactivity. Contact angle measurements revealed a clear hydrophilic-to-hydrophobic transition, with water contact angles increasing from 41° to over 100°. Moisture sensitivity was significantly reduced, with swelling ratio decreasing by up to 43 %, along with notable decreases in water solubility and vapor transmission. Thermo-mechanical performance also improved, with thermal degradation delayed by 15–20 °C, and tensile strength and flexibility increased to 41 MPa and 35 %, respectively, following SO and TTO incorporation. Self-cleaning behavior was demonstrated by high water contact angles and the films' ability to repel surface contaminants, supporting their potential for hygienic food packaging applications. Functional assessments further confirmed strong antioxidant activity, with radical scavenging reaching 74 %, alongside pronounced antibacterial effects against both E. coli and S. aureus . These findings highlight the potential of applying PDMS-based surface modification to CMC/NIHU/LS hybrid films to develop multifunctional, bioactive materials for food preservation. • CMC–NIHU–lignosulfonate biofilm for sustainable food packaging. • Spray-applied PDMS/silicone oil/tea tree oil coating for multifunctionality. • Coating increases hydrophobicity and reduces water vapor transmission. • AFM quantifies roughness and correlates with wettability and barrier properties. • Demonstrated self-cleaning, antimicrobial, and antioxidant activity.