Unlocking the potential of hydroxylated-chalcone-based photosensitive benzoxazines: synthesis, multifunctional properties and theoretical insights from density functional theory

This work pioneers the synthesis of a new class of benzoxazine monomers incorporating hydroxylated chalcone units (HAN-HB) using 2′-hydroxy-1′-acetonaphthone (HAN) and p-hydroxybenzaldehyde (HB) by following the Claisen–Schmidt condensation process. Three types of structurally varied bifunctional benzoxazines (Bz) were prepared using HAN-HB and paraformaldehyde separately with tyramine (ty), 3-amino-1-propanol (ap) and 2-(2-aminoethoxy)ethanol (aee) by adopting Mannich condensation. Both the HAN-HB and benzoxazine molecular structures were confirmed by different spectroscopic analyses. DSC analysis reveal that HAN-HB-ap benzoxazine showed the lowest T_p value of 214 °C. Poly(HAN-HB-ty) possesses the highest values of thermal decomposition temperature and percentage char yield. Further, all the polybenzoxazines exhibit self-extinguishing and good heat-resistant properties. In addition, the synthesised benzoxazines showed good anti-microbial behavior. Photosensitive properties of the benzoxazines were studied using UV–visible spectroscopic analysis and the results indicated that the synthesised benzoxazines exhibited both photo-isomerisation and photocrosslinking due to their inherent molecular rearrangement ability. An aggregation-caused quenching characteristic was observed for the benzoxazines through a fluorescence study. From the water contact angle study, it was inferred that all the poly(HAN-HB-Bz) exhibited a water repellent nature and showed a higher water contact angle of 151°. The corrosion-resistant behaviour of polybenzoxazines towards a mild steel surface was studied and the results obtained infer that these materials exhibit good protection efficiency. Density functional theory studies were performed for all the chalcone-based benzoxazines. The incorporation of hydroxyl groups not only improves hydrogen bonding interactions, enhancing thermal stability, but also introduces photo-reactivity. This dual functionality is not commonly reported in conventional benzoxazines. The results obtained from various studies suggest that the developed chalcone-based benzoxazines can be suitably exploited for advanced photosensitive coating applications. © 2025 Society of Chemical Industry.