Soybean oil-derived, non-isocyanate polyurethane–TiO2 nanocomposites with enhanced thermal, mechanical, hydrophobic and antimicrobial properties†

This study explores the development of non-isocyanate polyurethane (NIPU) composites incorporating bio-based soybean oil and TiO₂ nanoparticles (TNPs) with enhanced functional properties. Epoxidized soybean oil (ESBO) was converted to 5-membered cyclic carbonated soybean oil (CSBO) through CO₂ insertion under high temperature and pressure. TNPs (0%, 0.25%, 0.5%, and 1%) were incorporated into CSBO and cured with ethylenediamine (EDA). ATR-FTIR analysis confirmed the formation of urethane linkages in the NIPU films. The impact of TNPs on the physiochemical properties of the NIPU films was evaluated, including mechanical, thermal, surface wetting, and antimicrobial performance. Thermogravimetric analysis (TGA) indicated that TNPs did not significantly alter the degradation temperature of the NIPU films, whereas Differential Scanning Calorimetry (DSC) revealed that the glass transition temperature (T_g) of the NIPU films increased from 24 °C to 27 °C with TNP loading. Mechanical properties showed increased tensile strength with higher TNP content, while elongation at break decreased. Surface wettability measurements demonstrated that all composite films exhibited hydrophobic behavior, with contact angles ranging from 97° to 105°, higher than those of the bare NIPU films. Antimicrobial testing against Escherichia coli and Staphylococcus aureus demonstrated that TNP-loaded NIPU films exhibited significant antimicrobial activity against E. coli and antifouling properties against S. aureus. These bio-based NIPU composites offer a sustainable alternative to petroleum-based polyurethanes, with potential applications in eco-friendly adhesives, antimicrobial coatings, and protective surfaces, thereby contributing to greener solutions in materials science.