Flexible Ternary Combination of Gellan Gum, Sodium Carboxymethyl Cellulose, and Silicon Dioxide Nanocomposites Fabricated by Quaternary Ammonium Silane: Rheological, Thermal, and Antimicrobial Properties

[Image: see text] Gellan gum–sodium carboxymethyl cellulose (GC)-based composite films with various concentrations of silicon dioxide (SiO(2)) nanoparticles and octadecyldimethyl-(3-triethoxy silylpropyl)ammonium chloride (ODDMAC) were successfully prepared by the traditional solution casting method to improve the antimicrobial and water repellent properties. Fourier transform infrared (FT-IR) spectra confirm the formation of hydrogen bonds between the GC and nano-SiO(2). The microstructure and physicochemical properties were investigated by FT-IR, wide-angle X-ray diffraction, and scanning electron microscopy (SEM) analyses. The rheological properties of the GC–SiO(2) hydrogel were also characterized. The results show that the inclusion of SiO(2) nanoparticles significantly improved the viscosity and viscoelastic properties of the GC hydrogel. The GC–SiO(2) hydrogel exhibited shear-thinning behavior and its viscosity decreased at high shear rates. The storage and loss moduli of the GC composites increased as the frequency and SiO(2) concentration increased. The tensile strength and elongation at break of the GC composites increased by 75.9 and 62%, respectively, with the addition of SiO(2) and ODDMAC. In addition, nano-SiO(2) decreased the water vapor permeability and increased the hydrophobic properties of the GC–SiO(2) composites. Thermogravimetric analysis showed that the T(5%) loss was in the range of 99.4–128.6 °C and the char yield was in the range of 20.1–29.9%, which was significantly enhanced by the incorporation of SiO(2) nanoparticles. The GC–SiO(2) (ODDMAC) nanocomposites effectively shielded the UV light and exhibited high antimicrobial activity against six different pathogens. The simple and cost-effective GC–SiO(2) (ODDMAC) nanocomposites gained importance in food packaging and biomedical applications.