Eco-friendly nanostructured bio-polybenzoxazine films/coatings: One-pot green synthesis using Cardanol and Furfurylamine

This work highlights the in-situ green synthesis of thermally viable (250–300 °C) and antibacterial hydrophobic metal coordinated Cardanol formaldehyde aromatic polybenzoxazine [M(II)-CF-ArBz, whereas M(II)=Mn +2 , Zn +2 , Co +2 , and Ni +2 ] films using Cardanol (Col) and Furfurylamine (FAM). The effect of different transition metal ions and FAM on the overall performance of the developed films and coatings was investigated. The structure was elucidated with Fourier transform infrared spectroscopy (FTIR), Nuclear magnetic resonance NMR ( 1 H and 13 C), and X-ray photoelectron spectroscopy (XPS). The Powder X-ray diffraction (PXRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), revealed semi-crystalline behavior, nanostructures , and variation in morphology w.r.t. the metallic ions used. The different metal influences the nucleation and growth rate leading to different composite morphologies like ribbon (diameter 59 nm) in Co(II)-CF-ArBz, ultrafine spherical nanoparticles clusters of nano-dots (size 3 ± 1 nm) in Mn(II)-CF-ArBz, nanodisc (79 nm - 84 nm) in Zn(II)-CF-ArBz, and hollow tubular structure in case of Ni(II)-CF-ArBz. The improved antibacterial activity of developed M(II)-CF-ArBz films against various bacteria { Escherichia coli (MTCC 443), Pseudomonas aeruginosa (MTCC 2453) gram-negative, and Staphylococcus aureus (MTCC 902) and Bacillus subtilis (MTCC 736) gram-positive bacteria} were established via., growth inhibition and cell viability test. The physico-mechanical and surface wettability performance of M(II)-CF-ArBz coatings reveal mechanically more stable and hydrophobic than the respective virgin polybenzoxazine (CF-ArBz) coating. The relevance of the work is in the aspect of augmentation usage of renewable waste materials viz. Col and FAM, implementation of simple and in-situ route avoiding toxic residues, adoption of “Green Chemistry” principles, and highlighting the potential use of these sustainable films and coatings. • Sustainable development of nanostructured bio-polybenzoxazine films/coatings. • Utilization of fully bio-based resources, i.e., Cardanol and Furfurylamine and divalent transition metals. • Thermally stable (upto 270 ˚C) as well as flame-retardant films. • Improved mechanical strength of coatings upon metal incorporation. • Antibacterial active films against bacterial strains.