A facile cleaner approach towards the synthesis of silver-doped cardanol-based hydrophobic antimicrobial and anticorrosive polymeric coating material

This work reports the solvent, catalyst and cross-linker free green synthesis of silver (Ag)-doped cardanol-based multifunctional polymer nanocomposite (PNC) coatings. The interaction of Ag ions with the polymeric backbone and in-situ formation of nanoparticles (NP) was confirmed by various characterization techniques. The optimum curing temperature (120-170oC) and Ag concentration (1%) required for the free-standing film/coating with durable mechanical and chemical resistant properties in acidic/basic/salt solutions was studied. The high gel content (degree of crosslinking, 98%) and thermal stability up to 345 °C endorse the formulation of a well-cross-linked polymeric film/coating. XRD (approx. 27 nm) indicated the formation of crystalline silver nanoparticles within the polymer matrix, whereas SEM and TEM explored the distribution (200-700 nm). EIS studies for three weeks in 3.5% NaCl solution showed the exceptional corrosion inhibition efficiency (98-91%) of the coatings on steel substrate. The stable coating resistance value (MΩ.cm-2) throughout the study highlights the formation of a hydrophobic barrier with good resistance against the corrosive ions. Additionally, the potent antibacterial impact against Gram-positive, and Gram-negative bacteria, and the antifungal activity of the nanocomposite were attributed to the presence of Ag in the PNC. The multifunctional properties arise from the in-situ formed nanostructure and its synergistic effect with the biopolymer matrix projects its versatile industrial application.