Synthesis and Characterization of Sustainable Curcumin‐Based Bio‐benzoxazines for Antimicrobial and Anticorrosion Applications

Abstract In the current study, three novel bio‐based benzoxazines were produced from curcumin (CU), which reacts individually with three different primary amines such aniline (a), furfurylamine (ffa) and octadecylamine (oda) under suitable experimental conditions. FTIR and 1 H‐NMR spectra were used to confirm the molecular structure of synthesized curcumin based benzoxazine monomers (CU‐a, CU‐ffa and CU‐oda). It was found that the curing temperatures of the three benzoxazine monomers, CU‐a, CU‐ffa, and CU‐oda are 207 °C, 193 °C, and 199 °C respectively. According to theromogravimetric analysis (TGA) analysis, cured poly(CU‐a), poly(CU‐ffa), and poly(CU‐oda) have remaining char yields of 78, 77, and 55 %, respectively, and their corresponding limiting oxygen index (LOI) values are 49, 48, and 40, respectively, confirming that they have exceptional thermal stability and flame‐retardant qualities that are ideal for applications. The value of water contact angle of poly(CU‐a), poly(CU‐ffa) and poly(CU‐oda) are 131°, 135° and 137° respectively, which infer their excellent hydrophobicity. Results from corrosion and anti‐microbial studies ascertain that these curcumin based benzoxazines can be considered as efficient coating materials to protect the surfaces of mild steel specimen under adverse environmental conditions. Using density‐functional theory (DFT) band gap of the monomers has been calculated and found that CU‐a possesses the lower value of band gap of 2.9212 eV than other benzoxazines.